import java.util.*;

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 count = 0;

    boolean flg = true;

    while(flg) {
      count += k;

      if(a <= count && count <= b) {
        flg = true;
        break;
      }

      if(count > b) {
        flg = false;
        break;
      }
    }

    if(flg) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }

    sc.close();
  }
}
/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