#include <iostream>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);

    int n, res = 0;
    cin >> n;
    
    while (n > 0) {
        if (n % 10 == 0 || n % 10 == 5) {
            res++;
        } 
        
        n -= 7;
    }

    cout << res;

    return 0;
}