#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
	int flag = 0;//判断是否会超过两天
	int s, v;
	double t;//计算总共用时
	int h = 7, m = 60;
	cin >> s >> v;
	t = 10 + double(s) / double(v);
	while (t >= 60)
	{
		h--;
		t -= 60;
		if (h == 0&&flag==0)//到前一天
		{
			h += 24;
			flag++;
		}
		else if (h == 0 && flag == 1)//如果前一天也不行，就退出
		{
			return -1;
		}
	}
	//cout << "t=" << t << endl;
	m -= int(t+0.999999999);//t向上取整
	
	
	cout << setfill('0') << setw(2) << h << ":";
	cout<< setw(2) << setfill('0') << m;

	return 0;
}