#include<bits/stdc++.h>
using namespace std;
int s,v,hours=8,minits=0;
int main()
{
	cin>>s>>v;
	int t=s/v;
	hours-=t/60;
	minits-=t%60;
	if(minits<0)
	{
		hours-=(60-minits)/60;
		minits=60-minits;
	}
	if(minits>60)
	{
		hours++;
		minits-=60;
	}
	printf("%02d:%02d",hours,minits);
	return 0;
}