#include <iostream>

#include <cmath>

using namespace std;

bool prime(int x)

{

if (x < 2)

{

return false;

}

for (int i = 2; i <= sqrt(x); i++)

{

if (x % i == 0)

{

return false;

}

}

return true;

}

int main()

{

int n, count = 0;

cin >> n;

for (int x = 1; x + 2 <= n; x++)

{

int y = x + 2;

if (prime(x) == true and prime(y) == true)

{

count++;

}

}

cout << count;

}