#3和#5Wa了，求助！

#include<bits/stdc++.h>
using namespace std;
int main(){
    int s,v,HH=7,MM=50,t;
    cin>>s>>v;
    t=s/v;
    if(s%v!=0)t++;
    if(470>=t){
        HH-=t/60;
        if(t%60>MM){
            HH--;
            MM+=60-t%60;
        }else{
            MM-=t%60;
        }
    }else{
        HH+=24;
        HH-=t/60;
        if(t%60>MM){
            HH--;
            MM+=60-t%60;
        }else{
            MM-=t%60;
        }
    }    
    if(HH<10)cout<<'0';
    cout<<HH<<':'<<MM;
}