Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

2 ≤ |S| ≤ 26, where |S| denotes the length of S.

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If all the characters in S are different, print yes (case-sensitive); otherwise, print no.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io;
use std::collections::HashSet;

fn main() {
	let mut buf = String::new();
	io::stdin().read_line(&mut buf).expect("");
	let s:Vec<char> = buf.trim().chars().collect();
	let mut set = HashSet::new();
	let mut flag = true;
	for i in s {
		if !set.insert(i) {
			flag = false;
			println!("no");
			break;
		}
	}
	if flag {
		println!("yes");
	}
}