#[allow(dead_code)]
mod scanner {
    use std;
    use std::io::Read;
    use std::str::FromStr;
    use std::str::SplitWhitespace;
    pub struct Scanner<'a> {
        it: SplitWhitespace<'a>,
    }
    impl<'a> Scanner<'a> {
        pub fn new(s: &'a String) -> Scanner<'a> {
            Scanner {
                it: s.split_whitespace(),
            }
        }
        pub fn next<T: FromStr>(&mut self) -> T {
            match self.it.next().unwrap().parse::<T>() {
                Ok(v) => v,
                _ => panic!("Scanner error"),
            }
        }
        pub fn next_chars(&mut self) -> Vec<char> { self.next::<String>().chars().collect() }
        pub fn next_vec<T: FromStr>(&mut self, len: usize) -> Vec<T> {
            (0..len).map(|_| self.next()).collect()
        }
    }
    pub fn read_string() -> String {
        let mut s = String::new();
        std::io::stdin().read_to_string(&mut s).unwrap();
        s
    }
}

fn main() {
    let sc = scanner::read_string();
    let mut sc = scanner::Scanner::new(&sc);

    let n: usize = sc.next();
    let m: usize = sc.next();
    let p: usize = sc.next();
    let mut a = sc.next_vec::<usize>(n);
    for i in 0..n {
        while a[i] % p == 0 {
            a[i] /= p;
        }
    }
    a.sort();
    a.reverse();
    let ans = if a[0] == 1 {
        -1
    } else {
        let mut b = 0;
        let mut x = 1;
        while m >= x {
            x *= a[0];
            b += 1;
        }
        b
    };
    println!("{}", ans);
}