#include <iostream>

using namespace std;

int main()
{

    int P;
    cin >> P;
    int V;
    cin >> V;
    int K = P-V;
    int x = K/5;
    int y = K%5;
    int z = y/2;
    int a = y%2;
    int zbir = x+z+a;
    cout << zbir << endl;



    return 0;
}