#include <bits/stdc++.h> using namespace std;

int main() { int n, b; double c; cin >> n; b = (n - 2) * 180 ; c = b*1.0 / n; cout << fixed << setprecision(1) << c; return 0; }

#include using namespace std;

int main() { long long int a; scanf("%lld", &a); printf("%.1lf", 180.0 * (a - 2) / a); return 0; }

#include using namespace std;

int main() { int m, n; cin >> m >> n; cout << (n - m) * 30; return 0; }