#include <bits/stdc++.h>
using namespace std;
int main(){
    int h1,m1,h2,m2;
  while (cin>>h1>>m1>>h2>>m2){
    if (h1==0&&m1==0&&h2==0&&m2==0){
      break;
    }
    int a=h2*60+m2-h1*60-m1;
    if (a<0){
      a+=1440;
    }
    cout<<a<<endl;
  }
}