#include <iostream>
#include <iomanip>
using namespace std;


int main() {
    int h1,m1,h2,m2;

    cin >> h1;
    cin >> m1;
    cin >> h2;
    cin >> m2;

    while(h1!=0 || m1!=0 || h2!=0 || m2!=0){
        int min1=(60*h1 + m1);
        int min2=(60*h2 + m2);

        if(min2>min1){
              cout << min2-min1 << "\n";
        }else if(min1>min2){
              cout << 1440-min1+min2 << "\n";
        }else{
              cout << 0 << "\n";
        }
        cin >> h1;
        cin >> m1;
        cin >> h2;
        cin >> m2;
    }
    return 0;
}