#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

const INF: isize = 1_000_000_000_000_000_001;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let N = input!(usize);
    let P = input!(isize);
    let K = input!(usize);

    let mut dp = vec![isize::MIN; K + 1];
    dp[0] = P;

    for _ in 0..N {
        let T = input!(usize);
        let B = input!(isize);

        for i in (0..K).rev() {
            if dp[i] == isize::MIN {
                continue;
            }

            if T == 1 {
                let d = dp[i] + B;

                if d >= INF {
                    dp[i + 1] = std::cmp::max(dp[i + 1], INF);
                } else {
                    dp[i + 1] = std::cmp::max(dp[i + 1], d);
                }
            } else {
                let d = dp[i] * 2;

                if d >= INF {
                    dp[i + 1] = std::cmp::max(dp[i + 1], INF);
                } else {
                    dp[i + 1] = std::cmp::max(dp[i + 1], d);
                }
            }
        }
    }

    if dp[K] >= INF {
        writeln!(out, "-1");
    } else {
        writeln!(out, "{}", dp[K]);
    }
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}