#include <bits/stdc++.h>

using namespace std;

int main()
{
    long s,v;
    cin >> s >> v;
    long minute = ceil(s/v) + 10;
    long use_minute = minute%60;
    long use_hour = minute/60;
    long end_hour = 0;
    long end_minute = 0;
    if(use_hour>=0&&use_hour<=7)
    {
        if(use_minute == 0)
        {
            end_hour = 8 - use_hour;
            end_minute = 0;
        }
        else
        {
            end_hour = 8 - use_hour - 1;
            end_minute = 60 - use_minute;
        }
    }
    else if(use_hour == 8)
    {
        if(use_minute == 0)
        {
            end_hour = 0;
            end_minute = 0;
        }
        else
        {
            end_hour = 23;
            end_minute = 60 - use_minute;
        }
    }
    else if(use_hour>8)
    {
        if(use_minute == 0)
        {
            end_hour = 24 - use_hour%8;
            end_minute = 0;
        }
        else
        {
            end_hour = 24 - use_hour%8 - 1;
            end_minute = 60 - use_minute;
        }
    }
    cout << setfill('0') << setw(2) << end_hour << ":" << setw(2) << end_minute-1 << endl;
    return 0; 
}