#include <iostream>
//#include <bits/stdc++.h>

using namespace std;
long long sleden_deliv_so_5(long long x) {
    while(x % 5 != 0) {
        x++;
    }
    return x;
}
long long prethoden_deliv_so_5(long long x) {
    while(x % 5 != 0) {
        x--;
    }
    return x;
}
int main() {
    long long x, y;
    cin >> x >> y;

    long long minimum = ceil(20.0 * x / 19.0);
    long long maksimum = floor(10.0 * x / 9.0);

    if(maksimum > y) {
        maksimum = y;
    }

    if(minimum % 5 != 0){
        minimum = sleden_deliv_so_5(minimum);
    }
    if(maksimum % 5 != 0) {
        maksimum = prethoden_deliv_so_5(maksimum);
    }

    if(minimum > maksimum) {
        cout << 0 << endl;
    }
    else {
        cout << (maksimum - minimum) / 5 + 1 << endl;
    }


}