#include <iostream>

using namespace std;
int pay;

int main(){
    int res = 0;
    cin >> pay;
    int t = pay / 10;
    res += t;
    while(t >= 5){
        t -= 5;
        res += 2;
    }
    while(t >= 3){
        t -= 3;
        res++;
    }
    cout << res << endl;

    return 0;
}