#include <iostream>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <bitset>
#include <stack>
#include <algorithm>
#include <queue>
#include <string>
#include <cstring>
using namespace std;
int main(){
	int s,v;
	scanf("%d%d",&s,&v);
	int time=ceil(s*1.0/v)+10;
   //	cout<<time<<endl;
	int h=8,m=60;
	if(time%60==0){
		if(h<0) h=24+h;
		if(h<10) cout<<"0";
		cout<<h-time/60<<":00";
		return 0;
	}
	else if(time>60){
		     h=h-time/60-1;
		     m=m-time%60;
	} 
	else if(time<60){
		h--;
		m-=time;
	}
	if(h<0) h=24+h;
	if(h<10) cout<<"0";
	cout<<h<<":";
	if(time<10) cout<<"0"<<m;
	else cout<<m;
    return 0;
}