#include <stdio.h>
int main(){
int a,b;
if (scanf("%d %d",&a,&b)!=EOF){
//printf("%d %d",a,b);
int begin_hour = a/100;
int begin_minute = a%100;
int end_hour = b/100;
int end_minute = b%100;
int minute = end_minute -begin_minute;
int hour = end_hour - begin_hour;
if (minute<0){minute = minute+60;hour = hour-1;}
printf("%02d:%02d",hour,minute);
}else{
printf("input wrong");
}
return 0;
}
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