#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
#define REP(i, x) for(int i = 0; i < (x); i++)
template <class T>
inline bool chmax(T &a, T b) {
	if(a < b) {
		a = b;
		return true;
	}
	return false;
}

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

	vector a(n, 0), b(50, 0);
	REP(i, n) { scanf("%d", &a[i]); }

	int maxa = *max_element(a.begin(), a.end());

	REP(i, n) {
		int cnt = 1;
		while(a[i] % p == 0) a[i] /= p, cnt++;
		chmax(b[cnt], a[i]);
	}

	vector achive(3100, 1ll);
	REP(i, 3000) {
		REP(j, 50) {
			if(achive[i] <= m) chmax(achive[i + j], achive[i] * b[j]);
		}
	}

	REP(i, 3100) {
		if(achive[i] * maxa > m) {
			printf("%d\n", i + 1);
			return 0;
		}
	}

	puts("-1");

	return 0;
}