看起来木有神马问题啊 蒟蒻发问…… WA Code：

#include <bits/stdc++.h>
using namespace std;
long long  minn, hour;
double s, v;

int main() {
	cin >> s >> v;
	minn = ceil(s / v);
	if (minn > 470) {
		minn -= 470;
		hour = 24 - minn / 60;
		minn = 60 - minn % 60;
	} else {
		minn = 470 - minn;
		hour = minn / 60;
		minn = minn % 60;
	}
	if (hour < 10) {
		cout << "0";
	}
	cout << hour << ":";
	if (minn < 10) {
		cout << "0";
	}
	cout << minn;
	return 0;
}