import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	} main {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	} 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 = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		} int i = 1; int i = 1; i 1 i <= B i B i++ i++ i {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		} {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		} if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			} K*i < A K*i K i A {
				continue;
			} continue; if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			} K*i > B K*i K i B {
				System.out.println("NG");
				break;
			} System.out.println("NG") System.out.println System.out System System.out "NG" break; {
				System.out.println("OK");
				break;
			} System.out.println("OK") System.out.println System.out System System.out "OK" break; String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		// スペース区切りの整数の入力
		int A = sc.nextInt();
		int B = sc.nextInt();

		for(int i = 1; i <= B; i++) {
			if(K*i < A) {
				continue;
			} else if(K*i > B) {
				System.out.println("NG");
				break;
			} else {
				System.out.println("OK");
				break;
			}
		}
	}
}
