use std::io::{Read, stdin}; fn main() { let mut buf = String::new(); stdin().read_to_string(&mut buf).unwrap(); let mut tok = buf.split_whitespace(); let mut get = || tok.next().unwrap(); let s = get().as_bytes(); for t in b'A'..b'Z' { let c = s .iter() .filter(|&ch| *ch == t) .count(); if c > 1 { println!("NO"); return; } } println!("YES"); }