#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
const ll INF = (1LL << 61);
ll mod = (ll)1e9 + 7;

// i回操作をするときのxの値の最大値
ll dp[100010];
signed main() {
	ll N, M, P; cin >> N >> M >> P;
	vector<ll>A(N); for (int i = 0; i < N; i++)cin >> A[i];
	// 最後に掛けることができる
	ll t = 0;
	for (int i = 0; i < N; i++)t = max(t, A[i]);
	// 割る操作をi回するときの最大値
	vector<ll>m(62, 1);
	for (int i = 0; i < N; i++) {
		ll cnt = 0;
		while (A[i] % P == 0) {
			A[i] /= P;
			cnt++;
		}
		m[cnt] = max(m[cnt], A[i]);
	}
	dp[0] = 1;
	for (int i = 0; i < 10010; i++) {
		if (dp[i] * t > M) {
			cout << i + 1 << endl; return 0;
		}
		for (int j = 0; j <= 60; j++) {
			// 遷移
			dp[i + j + 1] = max(dp[i + j + 1], dp[i] * m[j]);
		}
	}
	cout << -1 << endl;
}