90分，求大佬帮调 TAT!!!

#include<iostream>
#include<cmath>
using namespace std;
	int s,v;
	int tm,ta;
	int a,b;
	double t;
int main(){

	cin >> s >> v;
    t=ceil(s/v)+10;
	if(t>480){
		t -= 480;
		tm = 24-t/60;
		ta = 59-(int)t%60;
		printf("%02d:%02d",tm,ta);
		
	}
    else {
    a=8-t/60;
	b=59-(int)t%60;
	printf("%02d:%02d",a,b); 	
}
    return 0;
}

本蒟蒻不知道错哪了！！