#include <stdio.h>
#include <algorithm>
#include <vector>
#include <deque>
#include <string>
#include <iostream>
using namespace std;
using ll = long long;

void solve();
int main() {
	solve();
#ifdef DBG
	while (true);
#endif
}

//446
void solve() {
	char A[6], B[6];
	scanf("%s %s", A, B);

	bool f = true;
	if (A[0] == '0' && A[1] != 0)
		f = false;
	if (B[0] == '0' && B[1] != 0)
		f = false;

	for (int i = 0; A[i]; i++)
		if (!('0' <= A[i] && A[i] <= '9'))
			f = false;
	for (int i = 0; B[i]; i++)
		if (!('0' <= B[i] && B[i] <= '9'))
			f = false;

	printf("%s\n", f ? "OK" : "NG");
}