#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5;
int n, m, a[N], cnt, tot;
vector<int>e[N], g[N];
int dfn[N], low[N]; //dfn[i]i节点的dfs序，low[i]i节点的回溯值
int book[N], id[N], sum[N], in[N], out[N]; //判断x是否在栈里
stack<int>stk;
int f[N];

void tarjan(int x) {
	low[x] = dfn[x] = ++cnt;
	stk.push(x);
	book[x] = 1;
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v]) {
			low[x] = min(low[x], dfn[v]);
		}
	}
	if (dfn[x] == low[x]) {
		++tot;
		int v;
		do {
			v = stk.top();
			stk.pop();
			book[v] = 0;
			id[v] = tot;
			sum[tot] += a[v];
		} while (v != x);
	}
}

void rebuild() {
	//重新建图
	for (int i = 1; i <= n; i++) {
		for (auto v : e[i]) {
			if (id[i] != id[v]) {
				g[id[i]].push_back(id[v]);
				in[id[v]]++;
			}
		}
	}
}

void topsort() {
	queue<int>q;
	int res = 0;
	for (int i = 1; i <= tot; i++) {
		if (in[i] == 0)
			q.push(i), f[i] = sum[i], res = max(res, f[i]);
	}

	while (!q.empty()) {
		int tmp = q.front();
		q.pop();
		for (auto v : g[tmp]) {
			in[v]--;
			if (in[v] == 0)
				q.push(v);
			f[v] = max(f[v], f[tmp] + sum[v]);
			res = max(res, f[v]);
		}
	}
	cout << res << endl;
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfn[i]) {
			tarjan(i);
		}
	}
	rebuild();
	topsort();
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5;
int cnt, tot, id[N], n, m, book[N], low[N], dfn[N];
int sum[N], out[N];
vector<int>e[N];
stack<int>stk;

void tarjan(int x) {
	dfn[x] = low[x] = ++cnt;
	stk.push(x);
	book[x] = 1;
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v]) {
			low[x] = min(low[x], dfn[v]);
		}
	}
	if (dfn[x] == low[x]) {
		++tot;
		int v;
		do {
			v = stk.top();
			stk.pop();
			sum[tot]++;
			id[v] = tot;

		} while (v != x);
	}
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfn[i])
			tarjan(i);
	}
	for (int i = 1; i <= n; i++) {
		for (auto v : e[i]) {
			//id[i]->id[v]
			if (id[i] != id[v]) {
				out[id[i]]++;
			}
		}
	}
	int res = 0, ans = 0;
	for (int i = 1; i <= tot; i++) {
		if (out[i] == 0) {
			res++;
			ans = sum[i];
		}
	}
	if (res > 1)
		cout << 0 << endl;
	else
		cout << ans << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 5;
#define int long long
int n, m, a[N], cnt, tot, s, k, pos[N];
vector<int>e[N], g[N];
int dfn[N], low[N]; //dfn[i]i节点的dfs序，low[i]i节点的回溯值
int book[N], id[N], sum[N], in[N], out[N]; //判断x是否在栈里
stack<int>stk;
int f[N];

void tarjan(int x) {
	low[x] = dfn[x] = ++cnt;
	stk.push(x);
	book[x] = 1;
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v]) {
			low[x] = min(low[x], dfn[v]);
		}
	}
	if (dfn[x] == low[x]) {
		++tot;
		int v;
		do {
			v = stk.top();
			stk.pop();
			book[v] = 0;
			id[v] = tot;
			sum[tot] += a[v];
		} while (v != x);
	}
}

void rebuild() {
	//重新建图
	for (int i = 1; i <= n; i++) {
		for (auto v : e[i]) {
			if (id[i] != id[v]) {
				g[id[i]].push_back(id[v]);
				in[id[v]]++;
			}
		}
	}
}

void topsort() {
	queue<int>q;
	int res = 0;
	q.push(id[s]);
	f[id[s]] = sum[id[s]];
	for (int i = 1; i <= tot; i++) {
		if (in[i] == 0 && i != id[s])
			q.push(i), f[i] = -1e9;
	}
	while (!q.empty()) {
		int tmp = q.front();
		q.pop();
		for (auto v : g[tmp]) {
			in[v]--;
			if (in[v] == 0)
				q.push(v);
			f[v] = max(f[v], f[tmp] + sum[v]);
		}
	}
}

signed main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
	}
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	for (int i = 1; i <= n; i++) {
		if (!dfn[i]) {
			tarjan(i);
		}
	}
	cin >> s >> k;
	for (int i = 1; i <= k; i++) {
		cin >> pos[i];
	}
	rebuild();
	topsort();
	int res = 0;
	for (int i = 1; i <= k; i++) {
		res = max(res, f[id[pos[i]]]);
	}
	cout << res << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int n, m;
vector<int>e[N], g[N];
int low[N], dfn[N], book[N], cnt, tot, siz[N], id[N];
stack<int>stk;
int dis[N << 1], vis[N << 1];

void tarjan(int x) {
	stk.push(x);
	dfn[x] = low[x] = ++cnt;
	book[x] = 1;
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v])
			low[x] = min(low[x], dfn[v]);
	}
	if (low[x] == dfn[x]) {
		int v;
		tot++;
		do {
			v = stk.top();
			stk.pop();
			book[v] = 0;
			id[v] = tot;
			siz[tot]++;
		} while (x != v);
	}
}

void rebuild() {
	for (int i = 1; i <= n; i++) {
		for (auto v : e[i]) {
			if (id[i] != id[v]) {
				g[id[i]].push_back(id[v]);
				g[id[v]].push_back(id[i] + tot);
				g[id[i] + tot].push_back(id[v] + tot);
			}
		}
	}
}

void spfa() {
	int res = 0;
	//dis[id[1]] = siz[id[1]];
	queue<int>q;
	q.push(id[1]);
	vis[id[1]] = 1;
	while (!q.empty()) {
		int tmp = q.front();
		q.pop();
		res = max(res, dis[tmp]);
		vis[tmp] = 0;
		for (auto v : g[tmp]) {
			int t = v % tot;
			if (t == 0)
				t = tot;
			if (dis[v] < dis[tmp] + siz[t]) {
				dis[v] = dis[tmp] + siz[t];
				if (!vis[v]) {
					vis[v] = 1;
					q.push(v);
				}
			}
		}
	}
	cout << max(siz[id[1]],dis[id[1] + tot]) << endl;
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfn[i])
			tarjan(i);
	}
	rebuild();
	spfa();

	return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 5e4 + 5,Mod=1e9;
int cnt, tot, n, m, dfn[N], low[N], book[N], id[N], siz[N], in[N];
stack<int>stk;
vector<int>e[N], g[N];
int vis1[N], vis2[N], ccnt[N];

void bfs() {
	queue<int>q;
	for (int i = 1; i <= n; i++) {
		if (in[i] == 0)
			q.push(i);
	}

	ccnt[1] = 1;
	book[1] = 1;
	//q.push(1);
	while (!q.empty()) {
		int tmp = q.front();
		q.pop();
		for (auto v : e[tmp]) {
			if (vis2[v] == 1) {
				ccnt[v] += ccnt[tmp];
				ccnt[v]%=Mod;
				--in[v];
				if (in[v] == 0)
					q.push(v);
			}
		}
	}
//	for (int i = 1; i <= n; i++)
//		cout << ccnt[i] << " ";
	cout << ccnt[2]%Mod << endl;
}

void tarjan(int x) {
	dfn[x] = low[x] = ++cnt;
	book[x] = 1;
	stk.push(x);
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v])
			low[x] = min(low[x], dfn[v]);
	}
	if (low[x] == dfn[x]) {
		tot++;
		int v;
		do {
			v = stk.top();
			stk.pop();
			book[v] = 0;
			id[v] = tot;
			siz[tot]++;
		} while (v != x);
	}
}

void dfs1(int x) {
	vis1[x] = 1;
	for (auto v : e[x]) {
		if (!vis1[v]) {
			dfs1(v);
		}
	}
}

void dfs2(int x) {
	vis2[x] = 1;
	for (auto v : g[x]) {
		if (!vis2[v])
			dfs2(v);
	}
}

signed main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
		in[y]++;
		g[y].push_back(x);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfn[i])
			tarjan(i);
	}
	//判断从1出发可以到达的dian
	dfs1(1);
	dfs2(2);
	if (vis1[2] == 0) {
		cout << 0 << endl;
		return 0;
	}
	for (int i = 1; i <= n; i++) {
		if (vis1[i] == 1 && vis2[i] == 1 && siz[id[i]] > 1) {
			cout << "inf" << endl;
			return 0;
		}
	}
	bfs();
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 5e5 + 5, Mod = 1e9;
int cnt, tot, n, m, dfn[N], low[N], book[N], id[N], siz[N], in[N];
stack<int>stk;
vector<int>e[N], g[N];
int vis1[N], vis2[N], ccnt[N];
map<pair<int, int>, int>mp;

void tarjan(int x) {
	dfn[x] = low[x] = ++cnt;
	book[x] = 1;
	stk.push(x);
	for (auto v : e[x]) {
		if (!dfn[v]) {
			tarjan(v);
			low[x] = min(low[x], low[v]);
		} else if (book[v])
			low[x] = min(low[x], dfn[v]);
	}
	if (low[x] == dfn[x]) {
		tot++;
		int v;
		do {
			v = stk.top();
			stk.pop();
			book[v] = 0;
			id[v] = tot;
			siz[tot]++;
		} while (v != x);
	}
}

signed main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		e[x].push_back(y);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfn[i])
			tarjan(i);
	}
	for (int i = 1; i <= n; i++) {
		for (auto v : e[i]) {
			if (id[i] != id[v] && mp.count({id[i], id[v]}) == 0) {
				mp[ {id[i], id[v]}] = 1;
				g[id[i]].push_back(id[v]);
				in[id[v]]++;
			}
		}
	}
	int sum = 0, flag = 0;
	for (int i = 1; i <= tot; i++) {
		if (in[i] == 0)
			sum++;
	}
	for (int i = 1; i <= tot; i++) {
		if (siz[i] == 1 && flag == 0 && in[i] == 0) {
			int T = 0;
			for (auto v : g[i]) {
				if (in[v] == 1) {
					T = 1;
				}
			}
			if (T == 0) {
				flag = 1;
			}
		}
	}
	sum -= flag;
	cout << fixed << setprecision(6) << double(n - sum) / double(n) << endl;
	return 0;
}