package test.demo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Yukicoder730 {
	public static void main(String[]args) throws IOException {
		List<String>list=new ArrayList<String>();
		list=Arrays.asList(input());
		Set set=new HashSet(list);
		if(set.size()==list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
		
		
		
	}
	
	
	public static  String[] input() throws IOException {
		BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
		
		String str=br.readLine();
		String[]str2=str.split("");
		
		return str2;
	}
}