#include<bits/stdc++.h>

using namespace std;

int s,v;
double t;
int minute,h;
double sum=480;//学校要求 

int main(){
	
	cin >> s >> v;
	t = ceil(s*1.0/v);
	sum -= t+10;
	while(sum>=60){
		sum -= 60;
		h++;
	}
	minute = sum;
	if(minute<0) minute += 60,h--;
	if(h<0) h += 24; 
	
	if(h<10) cout << 0;
	cout << h << ":";
	if(minute<10) cout << 0;
	cout << minute;
	
	return 0;
}