#include<bits/stdc++.h>
using namespace std;
#define int long long
#define M 1000000007
//#define M 998244353
const int inf=4e18;
int32_t main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);cout.tie(NULL);
	int k,a,b;cin>>k>>a>>b;
	for(int i=a;i<=b;i++)
	{
		if(i%k==0)
		{
			cout<<"OK\n";
			return 0;
		}
	}
	cout<<"NG\n";
}