Code

#include<iostream>
#define itn int
using namespace std;
int main() {
	int s,v;
	cin>>s>>v;
	int time=s/v;
	if(time*v<s)time++;
	time+=10;
	itn hour=time/60,minute=time%60;
	int sh=(8-hour+24)%24,sm=(60-minute)%60;
	if(sm!=0){
		sh--;
		sh=(sh+24)%24;
		if(sm>=10)
		cout<<sh<<":"<<sm;
		else
		cout<<sh<<":0"<<sm;
	}else
	cout<<sh<<":00";
	return 0;
}