WA， 70分求助

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
    int s, v, time;
    cin >> s >> v;
    time = 480 - 10;
    time -= ceil(s / v + 1);
    if (time / 60 < 10 || time % 60 < 10){
        if (time / 60 < 10 && time % 60 >= 10){
            cout << "0" << time / 60 << ":" << time % 60 << endl;
        }
        else if (time / 60 >= 10 && time % 60 < 10){
            cout << time / 60 << ":" <<"0"<< time % 60 << endl;
        }
        else if (time / 60 < 10 && time % 60 < 10){
            cout <<"0"<< time / 60 << ":" <<"0"<< time % 60 << endl;
        }
    }
    else if (time / 60 >= 10 && time % 60 >= 10){
        cout << time / 60 << ":" << time % 60 << endl;
    }
}

貌似好像都考虑到了，但跑不出来，是什么原因