#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

set<ll> prime_factor(ll n){
    set<ll> pf;
    //if(n == 1) pf.push_back(P(1, 1));
    for(ll i = 2; i*i <= n; i++){
        if(n%i == 0){
            while(n%i == 0){
                n /= i;
            }
            pf.insert(i);
        }
    }
    if(n != 1) pf.insert(n);
    return pf;
}

int main()
{
    ll n, m, p;
    cin >> n >> m >> p;
    vector<ll> a(n);
    rep(i, 0, n) cin >> a[i];
    sort(a.begin(), a.end());
    int cnt = 0;
    ll mx = 0;
    rep(i, 0, n){
        set<ll> pf = prime_factor(a[i]);
        if(pf.find(p) != pf.end()) continue;
        mx = max(mx, a[i]);
    }
    if(mx == 0){
        cout << -1 << endl;
        return 0;
    }
    ll x = 1;
    while(x <= m){
        cnt++;
        if(x*a[n-1] > m) break;
        else x *= mx;
    }
    cout << cnt << endl;
    return 0;
}