huyokkk

include <bits/stdc++.h>

using namespace std;

long long countSpecial(long long n) { if (n <= 0) return 0; long long a = 0, b = 0; if (n >= 1) a = (n - 1) / 5 + 1; if (n >= 4) b = (n - 4) / 5 + 1; return a + b; }

int main() { ios::syncwithstdio(false); cin.tie(nullptr);

long long L, R;
cin >> L >> R;
cout << countSpecial(R) - countSpecial(L - 1);

return 0;

}