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

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 C = input!(usize);
    let mut Y = input!(usize);

    if 100 * C > Y {
        writeln!(out, "can't exchange");
        return;
    }

    // 持っている通貨を特定する
    let mut c10000 = Y / 10000;
    Y -= 10000 * c10000;
    let mut c5000 = Y / 5000;
    Y -= 5000 * c5000;
    let mut c2000 = Y / 2000;
    Y -= 2000 * c2000;
    let mut c1000 = Y / 1000;
    Y -= 1000 * c1000;
    let mut c500 = Y / 500;
    Y -= 500 * c500;
    let mut c100 = Y / 100;
    Y -= 100 * c100;

    if c100 >= C {
        writeln!(out, "no exchange");
        return;
    }

    let d = C - c100;
    let a = ((d + 4) / 5) * 5 + c100;
    writeln!(out, "{}", a);
}

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())
            }
        }
    }
}