七十分，请问哪里出了问题？

#include<bits/stdc++.h>
using namespace std;
int main (){
    float s,v;
    int t,a,b,daymin;
    daymin=24*60+480;
    cin>>s>>v;
    t=ceil(s/v);
    if(t>=470){
        daymin=daymin-t-10;
        a=24-daymin/60;
        b=daymin%60;
        printf("%02d:%02d",a,b);
    }if(t<470){
        a=7-(t+10)/60;
        b=60-(t+10)%60;
        printf("%02d:%02d",a,b);
    }
    return 0;
}