#include<cmath>

#include<stdio.h>

#include<cstdio>

int main(){

	int s,v;

	int H,M;

	scanf("%d%d",&s,&v);

	double tt;

	tt=s/v;

	int HH,MM,h,m;

	h=(ceil(tt)+10)/60;

	//printf("%d\n",h);

	H=7-h;

	m=int(ceil(tt)+10)%60;

	if(m<1){

		M=0;

		H+=1;

		}

	 else M=60-m;

	//printf("%d   %d\n",H,M);

	if(H==24) H=0;

	if(H<10&&H>0){

		if(M>=10){

			printf("%s%d%s%d\n","0",H,":",M-1);}

		if(M<10){

			printf("%s%d%s%d\n","0",H,":0",M-1);}

	}

	else{

		HH=24-abs(H);

		if(HH>=10){

			if(M>=10){

			printf("%d%s%d\n",HH,":",M-1);}

			if(M<10){

			printf("%d%s%d\n",HH,":0",M-1);}

			}

		else{

			if(M>=10){

			printf("%d%s%d\n",HH,":",M-1);}

			if(M<10){

			printf("%d%s%d\n",HH,":0",M-1);}

			}	

	}



		

		

	//printf("%d %d\n",HH,H);

	return 0;

}

蒟蒻求助，80分...