import 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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    }
  }
} import java.util.*; util.* java 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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    } int i = 0; int i = 0; i 0 i < 1001 i 1001 i++ i++ i {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    } {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    } if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      } a <= k*i && k*i <= b a <= k*i a k*i k i k*i <= b k*i k i b {
        System.out.println("OK");
        break;
      } System.out.println("OK") System.out.println System.out System System.out "OK" break; if (i == 1000) {
        System.out.println("NG");
      } i == 1000 i 1000 {
        System.out.println("NG");
      } 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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    }
  }
} Main
import 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 = 0; i < 1001; i++) {
      if (a <= k*i && k*i <= b) {
        System.out.println("OK");
        break;
      }
      if (i == 1000) {
        System.out.println("NG");
      }
    }
  }
}
