import java.util.*;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int X = B % N;
    int goal = B - X;
    if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  }
} import java.util.*; util.* java class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int X = B % N;
    int goal = B - X;
    if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int X = B % N;
    int goal = B - X;
    if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int X = B % N;
    int goal = B - X;
    if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int A = sc.nextInt(); A sc.nextInt() sc.nextInt sc int B = sc.nextInt(); B sc.nextInt() sc.nextInt sc int X = B % N; X B % N B N int goal = B - X; goal B - X B X if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    } goal >= A && goal <= B goal >= A goal A goal <= B goal B {
      System.out.println("OK");
    } System.out.println("OK") System.out.println System.out System System.out "OK" {
      System.out.println("NG");
    } System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args
import java.util.*;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    int X = B % N;
    int goal = B - X;
    if (goal >= A && goal <= B) {
      System.out.println("OK");
    } else {
      System.out.println("NG");
    }
  }
}