use std::io::*;
use std::str::*;

const MOD: i32 = 1000000007;

fn read<T: FromStr>() -> Option<T> {
    let stdin = stdin();
    let s = stdin
        .bytes()
        .map(|c| c.unwrap() as char)
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok()
}

fn main() {
    let s: String = read().unwrap();
    let mut v: Vec<_> = s.chars().collect();
    v.sort();
    v.reverse();

    for i in 0..v.len() - 1 {
        print!("{}", v[i]);
    }
    println!("{}", v[v.len() - 1]);
}