RT，代码如下

#include <iostream>
#include <cmath>
using namespace std;
int s,v,minute=1920,h,m,t;
int main()
{
	cin>>s>>v;
	t=ceil(s/v*1.0)+11;
	minute-=t;
	minute%=1440;
	h=minute/60;
	m=minute%60;
	if(h<10)
	{
	    cout<<"0"<<h<<":";
	}
	else
	{
		cout<<h<<":";
	}
	if(m<10)
	{
	    cout<<"0"<<m<<endl;
	}
	else
	{
	    cout<<m<<endl;
	}
	return 0;
}

求大佬指正