#include<iostream>
#include<iomanip>
#include<algorithm>
using namespace std;
int s, v, t, c, m, Clock = 7, minute = 50;

int main()
{
	cin >> s >> v;
	t = s / v;
	if (t * v != s) t++;

	c = t / 60;
	m = t % 60;

	if (t >= 1430)
	{
		cout << "08:00" << endl;
		return 0;
	}
	
    Clock -= c;
	if (Clock < 0) Clock += 24;
	minute -= m;
	if (minute < 0) minute += 60;

	cout << setfill('0') << setw(2) << Clock << ":" << setfill('0') << setw(2) << minute;

	return 0;
}