50pts

#include<bits/stdc++.h>
using namespace std;
int s,v,t;
int main() {
	cin >> s >> v;
	t=ceil(s*1.0/v)+10; // ceil 向上取整 
	t=32*60-t;
	if(t<=24*60) {
		cout << fixed << setprecision(2) << 0 << t / 60 << ":" << t % 6;
	} else {
		cout << fixed << setprecision(2) << 0 << t / 60 - 24 << ":" << t % 60;
	}
	return 0;
}

大佬教我一下~~