#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
int main(){
	string a,b;
	cin>>a>>b;
	for(auto x:a)
		if(x<'0'||'9'<x)
			cout<<"NG"<<endl,exit(0);
	for(auto x:b)
		if(x<'0'||'9'<x)
			cout<<"NG"<<endl,exit(0);
	if(a[0]=='0'&&a!="0")
		cout<<"NG"<<endl,exit(0);
	if(b[0]=='0'&&b!="0")
		cout<<"NG"<<endl,exit(0);
	if(a.size()==5&&a>"12345")
		cout<<"NG"<<endl,exit(0);
	if(b.size()==5&&b>"12345")
		cout<<"NG"<<endl,exit(0);
	cout<<"OK"<<endl;
}