#include <iostream>
#include <cstdio>
using namespace std;
int main(){
	int s,u,mi=470,hour,minute;
	scanf("%d%d",&s,&u);
	mi-=s/u;
	if(s%u!=0){
		mi-=1;
	}
	hour=mi/60;
	minute=mi%60;
	if(minute<0){
		minute=60+minute;
		if(hour<=0){
			hour=24-hour;
		}
		hour--;
	} 
	printf("%.2d:%.2d",hour,minute);
	return 0;
}