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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		System.out.println("NG");
		
		

		
	} main {
		Scanner sc=new Scanner(System.in);
		
		int k=sc.nextInt();
		int a=sc.nextInt();
		int b=sc.nextInt();
		
		int c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		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 c=k; c k int flag=0; flag 0 while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		} c<=b c b {
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		} if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			} a<=c && c<=b a<=c a c c<=b c b {
				System.out.println("OK");
				System.exit(0);
				
			} System.out.println("OK") System.out.println System.out System System.out "OK" System.exit(0) System.exit System 0 c+=k c k 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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		System.out.println("NG");
		
		

		
	}
	
}
