#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    int s,v,t,h = 7,m = 50; 
    scanf("%d%d",&s,&v);
    if(s % v != 0){
    	t = s / v + 1;
	}else{
		t = s / v;
	}
	while(t >= 60){
		h--;
		t -= 60;
		if(h == 0 && t >= 60){
			h = 24; 
		}
	}
	m -= t;
	if(h < 10 && m < 10){
		printf("0%d:0%d",h,m);	
	}else if(h < 10){
		printf("0%d:%d",h,m);
	}else if(m < 10){
	    printf("%d:0%d",h,m);
	}else{
	    printf("%d:%d",h,m);
	}
    return 0;
}