#include<iostream>
using namespace std;
int main(){
    float s,v;
    cin>>s>>v;
    if(s==0||v==0){
    	cout<<"7:50";
	}
	int a=7,b=50;
	if(s/v>int(s/v)){
		b=b-int(s/v)-1;
	}
	else b=b-int(s/v);
	if(b<=0){
		a--;
		b+=60;
	}
	if(b<10)cout<<a<<"0:"<<b;
	cout<<a<<":"<<b;
}