#include <bits/stdc++.h>
using namespace std;
int main(){
	int s,v;
	cin>>s>>v;
	int t = ceil(s/v+10);
	int n = 8*60;
	n-=t;
	int h = n/60;
	int m = n%60;
	if(m<0){
		m+=60;
		h--;
	}
	if(h<0){
		h+=24; 
	}
	if(h<10)cout<<'0'<<h;
	else cout<<h;
	cout<<":";
	if(m<10)cout<<0<<m;
	else cout<<m;
	return 0;
}

倒数第二个测试点错误，望告知