ex1-1.java

import java.util.HashMap;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		HashMap<String, Boolean> count = new HashMap<String, Boolean>();
 
		Boolean flag = true;
		for (int i = 0; i < str.length(); i++) {
			String c = str.substring(i, i + 1);
			if (count.containsKey(c)) {
				flag = false;
			} else {
				count.put(c, true);
			}
		}
 
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
}