#include<bits/stdc++.h>
using namespace std;

double s,v,hour=8,minn=0;

int main()
{
    cin>>s>>v;
    if(ceil(s/v)>10) minn-=10;
	minn-=ceil(s/v);
	if(hour*60 + minn>=24*60) minn-=24*60;
	while(minn<0){
		minn+=60;
		hour--; 
	}
	if(hour<10){
		cout<<0;
	}
	cout<<hour<<":";
	if(minn<10){
		cout<<0;
	}
	cout<<minn;
    return 0;
}