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