#include <iostream>
using namespace std;
bool isprime(int a) {
for (int i = 2; i * i <= a; i++)
if (a % i == 0) return false;
return true;
}
int main() {
int N, cnt = 0;
cin >> N;
for (int i = 5; i <= N; i++)
if (isprime(i-2) && isprime(i)) cnt++;
cout << cnt;
return 0;
}
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