fn g() -> Vec<usize> {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	s.split_whitespace().flat_map(str::parse).collect()
}
fn main() {
	let v = g();
	let mut d = vec![0; v[2] + 1];
	d[0] = v[1];
	for _ in 0..v[0] {
		let t = g();
		for i in (0..v[2]).rev() {
			if d[i] < 1 {
				continue;
			}
			let p = if t[0] < 2 { d[i] + t[1] } else { d[i] * 2 };
			if p > 10usize.pow(18) {
				println!("-1");
				return;
			}
			d[i + 1] = d[i + 1].max(p);
		}
	}
	println!("{}", d[v[2]])
}