#include<iostream>

using namespace std;
int s,v,n=480,h,m,ans;
int main(){
	cin>>s>>v;
	n-=10;
	int num=0;
	if(s%v==0){
		num=s/v;
	}else{
		num=s/v+1;
	}
	n-=num;
	ans=n;
	while(ans>=60){
		ans-=60;
		h++;
	}

	cout<<"0"<<h<<":";
	if(ans>9){
		cout<<ans;
	}else{
		cout<<"0"<<ans;        
	}
	return 0;
}