#include<bits/stdc++.h>
using namespace std;
int minn;//最后一版orz 
double s,v;
int main(){
	cin>>s>>v;
	minn=ceil(s/v)+10;
	//cout<<minn<<endl;
	int hour,num;
	while(minn>=60){
		minn=minn-60;
		num++;
	}//num存小时数，minn存剩余分钟数 
	if(minn==0&&num<=8){
		cout<<"0"<<8-num<<":"<<"00";
		return 0;
	}//今天出发且整点 
	if(num<8){
		if(minn>=51){
			cout<<"0"<<8-num-1<<":0"<<60-minn;
			return 0;
		}
		else{
			cout<<"0"<<8-num-1<<":"<<60-minn;
			return 0;
		}
	}//今天出发不整点 
	if(num>=8&&num<=22){
		if(minn==0){
			cout<<24-(num-8)<<":"<<"00";
			return 0;
		}
	}//提前出发，小时数为二位，整点 
	if(num>=8&&num<22){
		if(minn>=51){
			cout<<24-(num-8)-1<<":"<<"0"<<60-minn;
			return 0;
		}
		else{
			cout<<24-(num-8)-1<<":"<<60-minn;
			return 0;
		}
	}//提前出发，小时数为二位，不整点 
	if(num>22){
		if(minn==0){
			cout<<"0"<<24-(num-8)<<":"<<"00";
			return 0;
		}
	}//提前出发，小时数为个位，整点
	if(num>=22){
		if(minn>=51){
			cout<<"0"<<24-(num-8)-1<<":"<<"0"<<60-minn;
			return 0;
		}
		else{
			cout<<"0"<<24-(num-8)-1<<":"<<60-minn;
			return 0;
		}
	}//提前出发，小时数为个位，整点
	return 0;
}

注释在代码里面 前三个点WA 求大佬看看吧。。。孩子调了一个小时了。。。