#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main(){
	long long s,v;
	cin>>s>>v;
	long long t=10+ceil(1.0*s/v);
	const int a=8*60;
	if(t<=a){
		cout<<0;
		int c=a-t;
		cout<<c/60<<':'<<c%60;
	}else{
		int c=t-a;
		const int a1=16*60;
		int c1=a1-c;
		if(c>14*60){
			cout<<0;
		}
		cout<<c1/60+8<<':'<<c1%60;
	}
	
	return 0;
}