#include<bits/stdc++.h>
using namespace std;
int main()
{
	ios::sync_with_stdio(false);
	int s,v;
	cin>>s>>v;
	int t=ceil(1.0*s/v)+10;
	int ans=(2880+480-t)%2880;
	int hh=ans/60,mm=ans%60;
	if(hh<10) cout<<0;
	cout<<hh<<":";
	if(mm<10) cout<<0;
	cout<<mm<<endl;
	return 0;
}