import java.util.*;

public class Main {
    /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    }
} import java.util.*; util.* java public class Main {
    /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    }
} Main /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    } main {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        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 int i = 0; i 0 while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        } i * K <= B i * K i K B {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        } int result = i * K; result i * K i K if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            } A <= result && result <= B A <= result A result result <= B result B {
                System.out.println("OK");
                return;
            } System.out.println("OK") System.out.println System.out System System.out "OK" return; i++ i System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args public class Main {
    /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    }
} public class Main {
    /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    }
} Main
import java.util.*;

public class Main {
    /**
     * AtCoder Beginner Contest 165
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

        int i = 0;
        while ( i * K <= B) {
            int result = i * K;
            if ( A <= result && result <= B) {
                System.out.println("OK");
                return;
            }
            i++;
        }
        System.out.println("NG");
    }
}
