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();
    for(int i=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    }
    System.out.print("NG");
  }
} import java.util.*; util.* java 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=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    }
    System.out.print("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=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    }
    System.out.print("NG");
  } main {
    Scanner sc = new Scanner(System.in);
    int K = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    for(int i=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    }
    System.out.print("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=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    } int i=A; int i=A; i A i<=B i B i++ i++ i {
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    } {
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    } if(i%K == 0){
        System.out.print("OK");
        return;
      } i%K == 0 i%K i K 0 {
        System.out.print("OK");
        return;
      } System.out.print("OK") System.out.print System.out System System.out "OK" return; System.out.print("NG") System.out.print 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 K = sc.nextInt();
    int A = sc.nextInt();
    int B = sc.nextInt();
    for(int i=A; i<=B; i++){
      if(i%K == 0){
        System.out.print("OK");
        return;
      }
    }
    System.out.print("NG");
  }
}