	#include <bits/stdc++.h>
	using namespace std;

	#define E "\n"
	#define int long long 
	#define f(i,l,n) for(int i=l;i<n;i++)

	

	int32_t main()
	{

	  

	  int k,a,b;
	  cin >> k >> a >> b;
	  if(a%k==0 || b%k==0 || ((b-a)/k)>0) cout<<"OK";
	  else cout<<"NG";

	}