#include <bits/stdc++.h>
using namespace std;
int main()
{
	long s,v;
	cin>>s>>v;
	long t=s/v+11;
	int minute=60-t%60;
	if(t==480) cout<<"00:00";
	if(t<480)//同一天 
	{
		if(t%60!=0&&minute>=10)
		cout<<"0"<<7-t/60<<":"<<minute;
		if(t%60!=0&&minute<10)
		cout<<"0"<<7-t/60<<":0"<<minute;
		if(t%60==0) 
		cout<<"0"<<8-t/60<<":"<<"00";
	}
	if(t>480&&t<=1320)//第二天下午 
	{
		if(t%60!=0&&minute>=10)
		cout<<31-t/60<<":"<<minute;
		if(t%60!=0&&minute<10)
		cout<<31-t/60<<":0"<<minute;
		if(t%60==0)  
		cout<<32-t/60<<":"<<"00";
	}
	if(t>1320)//第三天下午 
	{
		if(t%60!=0&&minute>=10)
		cout<<"0"<<31-t/60<<":"<<minute;
		if(t%60!=0&&minute<10)
		cout<<"0"<<31-t/60<<":0"<<minute;
		if(t%60==0) 
		cout<<"0"<<32-t/60<<":"<<"00";
	}
}