#include<bits/stdc++.h>
using namespace std;
int main(){
	int s,v,h=7,m=50;
	cin>>s>>v;
	while(s*1.0/v>60){
		h=h-1;
		if(h==0)
		h=24;
	}
	m=m-ceil(s*1.0/v);
	while(m<0){
		m=60+m;
		h=h-1;
	}
	if(h*1.0/10<1)
	cout<<"0";
	cout<<h<<":";
	if(m*1.0/10<1||m==0)
	cout<<"0"<<m;
	else
	cout<<m;
	return 0;
}