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();
		int s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
} 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();
		int s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
} 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 s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	} main {
		Scanner sc = new Scanner(System.in);
		
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	} 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 s =k; s k while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		} true {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		} if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			} a<=k && k <= b a<=k a k k <= b k b {
				System.out.println("OK");
				break;
			} System.out.println("OK") System.out.println System.out System System.out "OK" break; if(b<k) {
				System.out.println("NG");
				break;
			} b<k b k {
				System.out.println("NG");
				break;
			} System.out.println("NG") System.out.println System.out System System.out "NG" break; k+=s k s 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 s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
} 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 s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
} 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();
		int s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
}