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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            System.out.println("NG");
        }
	} main {
	    Scanner sc = new Scanner(System.in);
        int k = sc.nextInt();
        int a = sc.nextInt();
        int b = sc.nextInt();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            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 flg = 0; flg 0 for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        } int i=1; int i=1; i 1 i++ i++ i {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        } {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        } int num = k * i; num k * i k i if(num < a) continue; num < a num a continue; if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            } a <= num && b >= num a <= num a num b >= num b num {
                System.out.println("OK");
                flg = 1;
                break;
            } System.out.println("OK") System.out.println System.out System System.out "OK" flg = 1 flg 1 break; if(num > b) break; num > b num b break; if(flg == 0) {
            System.out.println("NG");
        } flg == 0 flg 0 {
            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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            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();
        int flg = 0;

        for(int i=1;; i++) {
            int num = k * i;
            if(num < a) continue;
            if(a <= num && b >= num) {
                System.out.println("OK");
                flg = 1;
                break;
            }
            if(num > b) break;
        }
        if(flg == 0) {
            System.out.println("NG");
        }
	}
}