use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let mut s: Vec<_> = s.split_whitespace().collect();
	(1..s.pop().unwrap().parse::<u8>().unwrap()).for_each(|_| s.push(s[1]));
	println!("{}", s.join("_"));
}