第9个测试点过不了，麻烦帮忙看看，非常感谢

#include<stdio.h>
int main()
{
    int s, t, hour ;
    scanf("%d", &s);
    scanf("%d", &t);
    int time, min;
    time = s / t + 10;
    if (time < 480) {
        hour = (480 - time) / 60;
        min = (480 - time) % 60-1;
    }
    else {
        hour = (1920 - time) / 60;  
        min = (1920 - time) % 60-1;
    }
    printf("%02d:%02d", hour, min);
    return 0;
}