import java.util.Scanner;

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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  }
} import java.util.Scanner; Scanner java.util 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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  }
} 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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  } main {
    Scanner sc = new Scanner(System.in);
    int K = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int K = sc.nextInt(); K 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 for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    } int i = 1; int i = 1; i 1 i <= 1000 i 1000 i++ i++ i {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    } {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    } if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      } K * i >= A && K * i <= B K * i >= A K * i K i A K * i <= B K * i K i B {
        System.out.println("OK");
        return;
      } System.out.println("OK") System.out.println System.out System System.out "OK" return; System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args 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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  }
} 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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  }
} Main
import java.util.Scanner;

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();

    for (int i = 1; i <= 1000; i++) {
      if (K * i >= A && K * i <= B) {
        System.out.println("OK");
        return;
      }
    }
    System.out.println("NG");

  }
}
