#include <iostream>
using namespace std;
 
int main() {
	int h1,m1,h2,m2;
	while(cin>>h1>>m1>>h2>>m2){
		if(h1==0 and m1==0 and h2==0 and m2==0){
			break;
		}
		int t1=h1*60+m1;
		int t2=h2*60+m2;
		int ans=t2-t1;
		if(t2-t1<0){
			ans=ans+1440;
		}
		cout<<ans<<endl;
	}
}
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