为什么只对了一半的分数，求解！！

#include <bits/stdc++.h>

using namespace std;

int divide(int a, int b) {
    return (a <= b) ? 1 : (a % b == 0 ? a / b : a / b + 1);//用了多少分钟
}

int main() {
    int s, v;
    scanf("%d %d", &s, &v);
    int min = divide(s , v);
    int all,hour,minn;
    all = 470 - min;//八个小时
    hour = all / 60;
    minn = all % 60;
    printf("0%d:%d", hour, minn);

    return 0;
}