#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vint;
typedef pair<int,int> pint;
typedef vector<pint> vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
const int MOD = 1e9 + 7;
const int INF = 1e9;

int main(void){
	string a, b;
	cin >> a >> b;
	

	rep(i, a.size()){
		if(!('0' <= a[i] && a[i] <= '9')){
			printf("NG\n");
			return 0;
		}
	}
	rep(i, b.size()){
		if(!('0' <= b[i] && b[i] <= '9')){
			printf("NG\n");
			return 0;
		}
	}
	// printf("ok\n");
	int na = stoi(a);
	int nb = stoi(b);
	if(!(0 <= na && na <= 12345)){
		printf("NG\n");
		return 0;
	}
	if(!(0 <= nb && nb <= 12345)){
		printf("NG\n");
		return 0;
	}

	if(a.size() > 1 && a[0] == '0'){
		printf("NG\n");
		return 0;
	}
	if(b.size() > 1 && b[0] == '0'){
		printf("NG\n");
		return 0;
	}
	printf("OK\n");

	return 0;
}