#include <bits/stdc++.h>
using namespace std;
int main(){
    int a, b;
    cin >> a >> b;
    if(a > 25 || b < 23){
        cout << 3 << endl;
        return 0;
    }
    if(a < 23){
        if(b > 25){
            cout << 3 << endl;
            return 0;
        }
        cout << b - 23 << endl;
        return 0;
    }
    if(b > 25)  cout << 25 - a << endl;
    else    cout << b - a - 1 << endl;
}