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: Wrong Answer)

fn main() {
    let mut s : Vec<char> = mylib::get_str().chars().collect();
    let mut r = true;
    for i in 0..s.len()-1 {
        if s[i] == s[i+1] {
            r = false;
            break;
        }
    }
    println!("{}", if r { "yes" } else { "no" })
}

mod mylib {
    // IO
    pub fn get_str() -> String {
        use std::io;
        let mut input = String::new();
        io::stdin().read_line(&mut input);
        input.as_str().trim().to_string()
    }
}