#[macro_export]
macro_rules! setup {
    { mut $input:ident: SplitWhitespace $(,)? } => {
        use std::io::Read;
        let mut buf = String::new();
        std::io::stdin().read_to_string(&mut buf).unwrap();
        let mut $input = buf.split_whitespace();
    };
}

#[macro_export]
macro_rules! parse_next {
    ($str_iter:expr) => {
        $str_iter.next().unwrap().parse().unwrap()
    };
}

fn main() {
    setup! { mut input: SplitWhitespace };

    let s: String = parse_next!(input);

    if !s.contains("pain") {
        println!("{}", -1);
        return;
    }

    let count = s.split("pain").nth(0).unwrap().matches("pon").count();

    if count < 2 {
        println!("{}", -1);
        return;
    }

    let ans = count - 1;

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