#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
long long a[200020];
int main() {
    long long n, m, p;
    cin >> n >> m >> p;
    long long ans = 1, m1 = 0;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        if (m1 < a[i]) {
            m1 = a[i];
        }
        while (a[i] % p == 0) {
            a[i] /= p;
        }
        if (ans < a[i]) {
            ans = a[i];
        }
    }
    m /= m1;
    if (m == 0) {
        cout << "1" << endl;
    }
    else if (ans == 1) {
        cout << "-1" << endl;
    }
    else {
        int co = 1;
        while (m >= 1) {
            m /= ans;
            co++;
        }
        cout << co << endl;
    }
}