use std::io;

fn main() {
    let mut input = String::new();
    io::stdin().read_line(&mut input).ok();

    let mut road = 1u64;
    input.trim().chars().for_each(|c| {
        road *= 2;
        if c == 'R' {
            road += 1;
        }
    });

    println!("{}", road);
}