#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

typedef long long ll;

const ll mod=1e9+7;

#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define rc(x)  return cout<<x<<"\n",0
#define sz(s)  (int) s.size()
#define pb push_back
#define mp make_pair
#define fr first
#define sc second

using namespace std;

ll k,l,r;

int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> k >> l >> r;
	ll largest = (r/k)*k;
	
	if (l<=largest) {
		cout << "OK\n";
	}
	else cout << "NG\n";

}
