最后三个WA，有大神帮忙解答一下吗？

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    double s,v;
    cin>>s>>v;
    int t2=ceil(s/v)+10;
        if(t2<=480)
        {
            int num1=(480-t2)/60;
            int num2=(480-t2)%60;
            if(num2<10)
                cout<<"0"<<num1<<":"<<"0"<<num2<<endl;
            else
                cout<<"0"<<num1<<":"<<num2<<endl;
        }
        else{
            int num3=24-(t2-480)/60;
            int num4=t2%60;
            if(num4<10)
            {
              if(num3<10)
              cout<<"0"<<num3<<":"<<"0"<<num4<<endl;
              else
                    cout<<num3<<":"<<"0"<<num4<<endl;
            }
            else{
                if(num3<10)
                cout<<"0"<<num3<<":"<<num4<<endl;
                else
                cout<<num3<<":"<<num4<<endl;
            }
            }
    return 0;
}