#include<iostream>
int main() {
freopen("TRATIEN.INP", "r", stdin);
freopen("TRATIEN.OUT", "w", stdout);
int M, N; std::cin >> M >> N;
int remain = N - M;
int n5 = remain / 5;
remain = remain % 5;
int n2 = remain / 2;
remain = remain % 2;
int n1 = remain;
std::cout << n1 + n2 + n5;
return 0;
}
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