fn get_line() -> String {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().to_string()
}

fn main() {
    println!("{}",
        get_line().as_bytes().iter().fold(0, |acc, &x|
            if x == b'n' {
                acc + 1
            }
            else {
                acc
            }
        )
    );
}