Envío 3168

Código

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.Set;

public class Main {

    public static void main(String[] args) throws Throwable {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        Set<Character> chars;
        for(String ln; (ln = in.readLine())!=null; ){
            chars = new HashSet<>();
            int size = ln.length();
            for(int i =0; i<size; i++)
                chars.add(ln.charAt(i));
            System.out.print(size == chars.size()?"yes":"no");
        }
    }
}