fn main() {
    let stdin = std::io::stdin();
    let mut rd = ProconReader::new(stdin.lock());

    let n: usize = rd.get();
    let m: u64 = rd.get();
    let p: u64 = rd.get();
    let a: Vec<u64> = rd.get_vec(n);

    let a: Vec<u64> = a.into_iter().filter(|&y| y != 1).collect();
    if a.is_empty() {
        println!("-1");
        return;
    }
    let max = *a.iter().max().unwrap();
    if max > m {
        println!("1");
        return;
    }
    let a: Vec<u64> = a
        .into_iter()
        .filter(|&y| {
            let mut y = y;
            while y % p == 0 {
                y /= p;
            }
            y != 1
        })
        .collect();
    if a.is_empty() {
        println!("-1");
        return;
    }
    let mut ans = std::u32::MAX;
    for y in a {
        let mut x = 1;
        let mut cnt = 0;
        while x <= m {
            if x * max > m {
                cnt += 1;
                break;
            }
            while x % p == 0 {
                x /= p;
                cnt += 1;
            }
            x *= y;
            cnt += 1;
        }
        ans = ans.min(cnt);
    }
    assert!(ans < std::u32::MAX);
    println!("{}", ans);
}

pub struct ProconReader<R> {
    r: R,
    line: String,
    i: usize,
}

impl<R: std::io::BufRead> ProconReader<R> {
    pub fn new(reader: R) -> Self {
        Self {
            r: reader,
            line: String::new(),
            i: 0,
        }
    }
    pub fn get<T>(&mut self) -> T
    where
        T: std::str::FromStr,
        <T as std::str::FromStr>::Err: std::fmt::Debug,
    {
        self.skip_blanks();
        assert!(self.i < self.line.len());
        assert_ne!(&self.line[self.i..=self.i], " ");
        let line = &self.line[self.i..];
        let end = line.find(' ').unwrap_or_else(|| line.len());
        let s = &line[..end];
        self.i += end;
        s.parse()
            .unwrap_or_else(|_| panic!("parse error `{}`", self.line))
    }
    fn skip_blanks(&mut self) {
        loop {
            let start = self.line[self.i..].find(|ch| ch != ' ');
            match start {
                Some(j) => {
                    self.i += j;
                    break;
                }
                None => {
                    self.line.clear();
                    self.i = 0;
                    let num_bytes = self.r.read_line(&mut self.line).unwrap();
                    assert!(num_bytes > 0, "reached EOF :(");
                    self.line = self.line.trim_end_matches(&['\r', '\n'][..]).to_string();
                }
            }
        }
    }
    pub fn get_vec<T>(&mut self, n: usize) -> Vec<T>
    where
        T: std::str::FromStr,
        <T as std::str::FromStr>::Err: std::fmt::Debug,
    {
        (0..n).map(|_| self.get()).collect()
    }
}