#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y;
  scanf("%d %d", &x, &y);
  long long ans = 0;
  for (int val = 1; val <= x; ++val) {
    ans += (int)floor((y - (5 - (val % 5))) / 5.0) + 1;
  }
  cout << ans << endl;
  return 0;
}
