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

vector<int> split(int x) {
	vector<int> ans;
	while (x != 0) {
		ans.push_back(x % 10);
		x /= 10;
	}
	return ans;
}

bool isprime(int x) {
	for (int f = 2; f * f <= x; f++) {
		if (x % f == 0)
			return false;
	}

	return true;
}

bool check(int x) {
	vector<int> tmp = split(x);

	for (int i = 0; i < tmp.size(); i++) {
		if (tmp[i] != tmp[tmp.size() - 1 - i]) {
			return false;
		}
	}

	return isprime(x);
}

int main() {
	int n;
	cin >> n;

	int ans = 0;

	for (int i = 11; i <= n; i++) {
		if (check(i))
			ans++;
	}

	cout << ans;

	return 0;
}