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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	}

} 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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	}

} 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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	} main {


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

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

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

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		} int i=1; int i=1; i 1 i<1000 i 1000 i++ i++ i {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		} {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		} if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			} tmpK >= A && tmpK <= B tmpK >= A tmpK A tmpK <= B tmpK B {
				System.out.println("OK");
				return;
			} System.out.println("OK") System.out.println System.out System System.out "OK" return; if(tmpK > B) {
				System.out.println("NG");
				return;
			} tmpK > B tmpK B {
				System.out.println("NG");
				return;
			} System.out.println("NG") System.out.println System.out System System.out "NG" return; tmpK += K tmpK K 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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	}

} 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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	}

} 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();

		if(K > B) {
			System.out.println("NG");
			return;
		}


		int tmpK = K;
		for(int i=1; i<1000; i++) {

			if(tmpK >= A && tmpK <= B) {
				System.out.println("OK");
				return;
			}

			if(tmpK > B) {
				System.out.println("NG");
				return;
			}
			tmpK += K;

		}

	}

}
