#include<cstdio>
#include<cmath>
using namespace std;
int s, v, time, hh, mm;
int main() {
	scanf("%d%d", &s, &v);
	time = 60 * (24 + 8) - ceil((1.0 * (s / v)) + 10);
	hh = (time / 60) % 24;
	mm = time % 60;
	printf("%02d:%02d\n", hh, mm);
	return 0;
}

输入100 99，输出07:49，而非07:48，十分困惑，求解