#include <bits/stdc++.h>
using namespace std;
int main(){
	int s,v,time;
	cin>>s>>v;
	if (s%v==0){
		time=s/v;
	}
	else{
		time=s/v+1;
	}
	time+=10;
	if (time<60){
		cout<<"07:"<<60-time;
	}
	if (time==60){
		cout<<"07:00";
	}
	if (time>60){
		if (time<480){
			int k=time/60;
			int q=time%60;
			if (q==0){
				cout<<"0"<<8-k<<":00";
			}
			else{
				cout<<"0"<<8-k-1<<":"<<60-q;
			}
		}
		if (time==480){
			cout<<"00:00";
		}
		if (time>480){
			time-=480;
			if (time<60){
				cout<<"23:"<<60-time;
			}
			if (time==60){
				cout<<"23:00";
			}
			if (time>60){
				int k=time/60;
				int q=time%60;
				if (q==0){
					if (k<15){
						cout<<24-k<<":00";
					}
					else{
						cout<<"0"<<24-k<<":00";
					}
				}else{
					if (k<15){
						cout<<24-k-1<<":"<<60-q;
					}
					else{
						cout<<"0"<<24-k-1<<":"<<60-q;
					}
				}
			}
		}
	}
	return 0;
}