import java.util.*;
import java.math.BigInteger;

public class Main {
  public static void main (String[] args) {
    Scanner sc = new Scanner(System.in);
    int K = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int x = A / K;
    int X = (x+1)*K;
    
    if(A == x*K) {
      System.out.println("OK");
    } else if(A<X && X<=B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz