#include <iostream>
#include <string>

using namespace std;
int main()
{
	string s[2];
	bool flag = false;
	cin >> s[0] >> s[1];
	for (int i = 0; i < 2; i++)
	{
		if (s[i].size()>=2 && s[i].at(0) == '0') flag = true;
		else
		{
			for (int j = 1; j < s[i].length(); j++)
			{
				if (!(s[i].at(j) >= 48 && s[i].at(j) <= 57))
				{
					flag = true;
				}
			}
		}
	}

	cout << (flag ? "NG" : "OK") << endl;
	return 0;
}