#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
//-------------------------------------------------------

string A,B;

int ok(string A) {
	int i;
	char buf[202];
	for(i=0;i<=12345;i++) {
		sprintf(buf,"%d",i);
		if(buf==A) return 1;
	}
	return 0;
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>A>>B;
	if(ok(A)&&ok(B)) _P("OK\n");
	else _P("NG\n");
	
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n';
	FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	solve(); return 0;
}