#include<iostream>
#include<cmath>
using namespace std;

int main(){
	int t;
	int time[2]={7,50};
	double s,v;
	cin>>s>>v;
	t=ceil(s/v);
	time[1]-=t;
	while(time[1]<0){
		time[1]+=60;
		time[0]--;
	}
	if(time[0]<0) time[0]+=24;
	if(time[0]<10) cout<<"0"<<time[0]<<":"<<time[1];
	else  cout<<time[0]<<":"<<time[1];
}