#include<bits/stdc++.h>
using namespace std;
int main()
{
	int s,v;
	cin>>s>>v;
	int t=ceil(s/v*1.0+10);
	while(t>=1440)
	t=t-1440;
	if(t<=480)
	{
		int h=floor(t/60.0);
		int min=t-60*h;
		cout<<"0"<<7-h<<":";
		if(min>=50)
		cout<<"0"<<59-min;
		else 
		cout<<59-min;
	}
	else
	{
		t=t-480;
		int h=floor(t/60.0);
		int min=t-60*h;
		if(h>=20)
		cout<<"0"<<23-h<<":";
		else
		cout<<23-h<<":";
		if(min>=50)
		cout<<"0"<<59-min;
		else
		cout<<59-min;
	}
	return 0;
}