#include <bits/stdc++.h>
using namespace std;
int s,v;
int h = 7,m = 60;
int main()
{
    cin >> s >> v;
    m -= ((s / v + 1) % 60);
    int t = (s / v + 1) / 60;
    m -= 10;
    h -= t;
    if (m < 10)
    {
    	cout << 0 << h << ":" << 0 << m;
	}
	else
	{
		cout << 0 << h << ":" << m;
	}
	return 0;
}