#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pint = pair<int,int>;

int f(int n, int p) {
	while(n % p == 0) n /= p;
	return n;
}

int main()
{
	int n, m, p; cin >> n >> m >> p;
	vector<int> a(n);
	for(auto &i : a) cin >> i;
	for(auto &i : a)i = f(i, p);
	int nax = *max_element(a.begin(), a.end());
	if(m == 1) {
		cout << 0 << endl; return 0;
	}
	if(nax == 1) {
		cout << -1 << endl; return 0;
	}

	ll ret = 1;
	int cnt = 0;
	while(ret <= m) {
		cnt++;
		ret *= nax;
	}
	cout << cnt << endl;

}