//“Make it work, make it right, make it fast.” – Kent Beck
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double dd;
const int siz = 1e6 + 5;
const int MOD = 1e9 + 7;
#define endl '\n'
#define deb(x) cout << #x << " = " << x << endl;

void solve(){
	int k;
	cin >> k;
	int a, b;
	cin >> a >> b;
	int s = a/k;
	bool flag = false;
	while(s <= b){
		int x = s*k;
		if( x >= a && x <= b){
			flag = true;
			break;
		}
		s++;
	}
	if(flag)
		cout << "OK";
	else
		cout << "NG";
}

int main(){
	#ifndef RAY
		//freopen("input.txt", "r", stdin);
	#endif
		ios::sync_with_stdio(false);
		cin.tie(nullptr);
		int t = 1;
		//cin >> t;
		while(t--){
			solve();
		}
	return 0;
}	
