fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let s: Vec<_> = s.split("pain").collect();
	let p = s[0].split("pon").count() as i64;
	println!("{}", if s.len() < 2 || p < 3 { -1 } else { p - 2 })
}