#include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     if (n > m) swap(m, n);     long long cc = 0;     for (int i = 1; i <= n; i++) {       cc += (m + i) / 5 - i / 5;     }     cout << cc << endl;     return 0;   }   