use std::collections::HashMap;

fn main() {
    let stdin = std::io::stdin();
    let mut line = String::new();
    stdin.read_line(&mut line).unwrap();
    let mut line = String::new();
    stdin.read_line(&mut line).unwrap();
    let line = line.trim();
    let mut counter = HashMap::new();
    for c in line.chars() {
        *counter.entry(c).or_insert(0) += 1;
    }
    let mut ret = String::new();
    for c in 'A'..='Z' {
        ret += &format!("{}", counter.get(&c).cloned().unwrap_or(0));
    }
    println!("{}", ret);
}