static LIM: i64 = 1_000_000_000_000_000_000;

fn main() {
    // input
    let mut sc = Scanner::new(std::io::stdin().lock());
    let n: usize = sc.next();
    let p: i64 = sc.next();
    let k: usize = sc.next();
    let tb: Vec<(u8, i64)> = (0..n)
        .map(|_x| (sc.next::<u8>(), sc.next::<i64>()))
        .collect();

    // answer
    let ans = solve(n, p, k, tb).unwrap_or(-1);

    // output
    fastout(&ans.to_string());
}

fn solve(n: usize, p: i64, k: usize, tb: Vec<(u8, i64)>) -> Option<i64> {
    let mut dp = vec![vec![-1; k + 1]; n + 1];
    dp[0][0] = p;
    for (i, &(t, b)) in tb.iter().enumerate() {
        for j in 0..=k {
            if dp[i][j] > 0 && dp.get(i + 1).is_some() {
                dp[i + 1][j] = dp[i + 1][j].max(dp[i][j]);
                if dp[i + 1].get(j + 1).is_some() {
                    match t {
                        1 => {
                            dp[i + 1][j + 1] = dp[i][j] + b;
                        }
                        2 => {
                            dp[i + 1][j + 1] = dp[i][j] * 2;
                        }
                        _ => unreachable!(),
                    }
                    if dp[i + 1][j + 1] > LIM {
                        return None;
                    }
                }
            }
        }
    }
    Some(dp[n][k])
}

// snippet
struct Scanner<R: std::io::BufRead> {
    reader: R,
    buf: Vec<u8>,
    pos: usize,
}
impl<R: std::io::BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Scanner {
            reader,
            buf: Vec::new(),
            pos: 0,
        }
    }
    #[allow(dead_code)]
    fn with_capacity(reader: R, capacity: usize) -> Self {
        Scanner {
            reader,
            buf: Vec::with_capacity(capacity),
            pos: 0,
        }
    }
    fn next<T: std::str::FromStr>(&mut self) -> T
    where
        T::Err: std::fmt::Debug,
    {
        if self.buf.is_empty() {
            self.read_next_line();
        }
        let mut start = None;
        loop {
            if self.pos == self.buf.len() {
                break;
            }
            match (self.buf[self.pos], start.is_some()) {
                (b' ', true) | (b'\n', true) => break,
                (_, true) | (b' ', false) => self.pos += 1,
                (b'\n', false) => self.read_next_line(),
                (_, false) => start = Some(self.pos),
            }
        }
        let elem = unsafe { std::str::from_utf8_unchecked(&self.buf[start.unwrap()..self.pos]) };
        elem.parse()
            .unwrap_or_else(|_| panic!("{}", format!("failed parsing: {}", elem)))
    }
    fn read_next_line(&mut self) {
        self.pos = 0;
        self.buf.clear();
        if self.reader.read_until(b'\n', &mut self.buf).unwrap() == 0 {
            panic!("Reached EOF");
        }
    }
}

fn fastout(s: &str) {
    use std::io::{stdout, BufWriter, Write};
    let mut out = BufWriter::new(stdout().lock());
    writeln!(out, "{}", s).expect("failed to write data.");
}