import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] word = S.split("");
        int check = 0;
        for(int i = 0;i<word.length;i++){
            for(int k = 0;k<word.length;k++){
                if(i != k&&word[i] == word[k]){
                    check++;
                }
            }
        }
        if(check == 0){
            System.out.print("YES");
        }else{
            System.out.print("NO");
        }
    }
}