#include <iostream>
#include <stdio.h>
#include <string>
#include <algorithm>
#include <vector>
#include <math.h>
#include <numeric>
#include <queue>
#include <numeric>
#include <iomanip>
#include <sstream>
#include <cmath>
#include <map>
#include <functional>
#include <limits>
#include <set>
#include <stack>
#define rep(i,a,b) for((i)=a;i<(int)(b);i++)
#define max(a,b) ((a) < (b) ? (b) : (a))
#define min(a,b) ((a) > (b) ? (b) : (a))
#define AAA (1000000007)

using namespace std;
typedef long long ll;
typedef unsigned long long ull;



ll gcd(ll a, ll b) {
	if (b == 0)return a;
	return gcd(b, a % b);
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}



int main() {
	string S;
	int i, j, k;
	//ll N, M, K;
	int N, M, K;
	
	cin >>K >> N >> M ;
	rep(i, N, M + 1) {
		if (i % K == 0) {
			cout << "OK";
			return 0;
		}
	}
	cout << "NG";
	return 0;
	
}