#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n, m, p; cin >> n >> m >> p;
  vector<int> a(n); REP(i, n) cin >> a[i];
  sort(ALL(a));
  map<int, int> b;
  for (int ai : a) {
    int d = 0;
    while (ai % p == 0) {
      ai /= p;
      ++d;
    }
    if (ai > 1 && (b.count(d + 1) == 0 || b[d + 1] < ai)) b[d + 1] = ai;
  }
  if (b.empty() && a.back() <= m) {
    cout << "-1\n";
    return 0;
  }
  vector<ll> dp(1, 1);
  for (int ans = 0; ; ++ans) {
    if (dp[ans] * a.back() > m) {
      cout << ans + 1 << '\n';
      return 0;
    }
    for (auto [op, ai] : b) {
      if (dp.size() <= ans + op) dp.resize(ans + op + 1, 1);
      chmax(dp[ans + op], dp[ans] * ai);
    }
  }
}