import java.util.*;

public class Main{
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	final int X = sc.nextInt();
    int X2 = X;
    int A = sc.nextInt();
    int B = sc.nextInt();
      while(X2 <= 1000){
        if(X2 >= A && X2 <= B){
          System.out.println("OK");
          return;
        }
        X2 += X;
        
      }
      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