#include<iostream>
#include<cmath>
#include<cstring>
#include<bits/stdc++.h>
#include<algorithm>
using namespace std;
int main()
{
	int s,u;
	cin>>s>>u;
	int time=(8*60+24*60)-10;
	int use=ceil(s/u*1.0);
	time-=use;
	if(time>24*60)
	{
		time-=24*60;
	}
	printf("%02d:%02d",time/60,time%60-1);
    return 0;
}