#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;



signed main() {
	ll N, M, P; cin >> N >> M >> P;
	vector<ll>A(N); for (int i = 0; i < N; i++)cin >> A[i];
	sort(A.rbegin(), A.rend());
	for (int i = 0; i < N; i++) {
		if (A[i] > M) {
			cout << 1 << endl; return 0;
		}
		if (A[i] % P != 0) {
			ll x = 1;
			ll ans = 0;
			while (true) {
				if (x > M)break;
				ans++;
				x *= A[i];

			}
			cout << ans << endl; return 0;
		}
	}
	cout << -1 << endl;
}