11677

#include<stdio.h>
int main()
{
    int h1,m1,h2,m2,h,m,ans;
    while(scanf("%d%d%d%d",&h1,&m1,&h2,&m2)==4)
    {
        if(h1==0&&m1==0&&h2==0&&m2==0)
            break;
        else
        {
            h=h2-h1;
            m=m2-m1;

            if(m<0)
            {
                m=m+60;
                h=h-1;
            }
            if(h<0)
            {
                h=h+24;
            }
            ans=(h*60)+m;

        }
        printf("%d\n",ans);
    }
    return 0;
}