#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    double s = 0; //米
    double v = 0; //分钟
    cin >> s >> v;
    int time = s / v + 10;//出行时间为分钟制
    if (s % v != 0) //出行时间不为整数时，向上取整
    {
        time++;
    }

    if (time / 60 < 8)
    {
        cout << "0" << 7 - ceil(time / 60) << ":" << 60 - time % 60;
    }
    else if (time / 60 == 8)
    {
        cout << "00:00" << endl;
    }
    else //总出行时间超过8小时
    {
        int left_time = time - 8 * 60;
        int left_time_H = left_time / 60;
        left_time_H = floor(left_time_H);

        int left_time_M = left_time % 60;

        if (left_time % 60 >= 50)// 分钟要补 0
        {
            if (left_time_H > 14) //小时也要补 0
            {
                cout << "0" << 23 - left_time_H << ":" << "0" << 59 - left_time_M << endl;
            }
            else //小时不需要补 0
            {
                cout << 23 - left_time_H << ":" << "0" << 59 - left_time_M << endl;
            }
        }
        else if (left_time_H > 14) //小时要补 0
        {
            if (left_time % 60 >= 50)// 分钟也要补 0
            {
                cout << "0" << 23 - left_time_H << ":" << "0" << 59 - left_time_M << endl;
            }
            else// 分钟不要补 0
            {
                cout << "0" << 23 - left_time_H << ":" << 59 - left_time_M << endl;
            }
        }
    }
}