/* -*- coding: utf-8 -*-
 *
 * 1330.cc:  No.1330 Multiply or Divide - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const int INF = 1 << 30;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m, p;
  scanf("%d%d%d", &n, &m, &p);

  int maxa = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d", as + i);
    if (maxa < as[i]) maxa = as[i];
  }

  if (maxa > m) { puts("1"); return 0; }

  int k = (m + maxa - 1) / maxa;
  int minc = INF;
  for (int i = 0; i < n; i++) {
    int b = as[i], dc = 1;
    while (b % p == 0) b /= p, dc++;
    if (b == 1) continue;

    ll x = 1;
    int c = 1;
    while (x <= k) x *= b, c += dc;
    if (minc > c) minc = c;
  }

  printf("%d\n", (minc < INF) ? minc : -1);
  return 0;
}