import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    }
} Main public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    } main {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"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 boolean ans = false; ans false int n = 0; n 0 while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        } n <= B n B {
            if(n >= A){
                ans = true;
            }
            n += K;
        } if(n >= A){
                ans = true;
            } n >= A n A {
                ans = true;
            } ans = true ans true n += K n K System.out.println(ans?"OK":"NG") System.out.println System.out System System.out ans?"OK":"NG" ans "OK" "NG" String[] args args public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    }
} public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        boolean ans = false;
        int n = 0;

        while(n <= B){
            if(n >= A){
                ans = true;
            }
            n += K;
        }

        System.out.println(ans?"OK":"NG");
    }
}
