/**
*    author:  shu8Cream
*    created: 08.01.2021 21:06:40
**/

#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i=0; i<(n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using P = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,m,p;
    cin >> n >> m >> p;
    vector<P> a(n);
    rep(i,n){
        cin >> a[i].first;
        while(a[i].first%p==0){
            a[i].first/=p;
            a[i].second++;
        }
    }
    sort(all(a));
    int tmp = 1;
    int ans = 0;
    if(a[n-1].first==1){
        cout << -1 << endl;
        return 0;
    }
    while(tmp<m){
        tmp*=a[n-1].first;
        ans+=a[n-1].second+1;
    }
    cout << ans-a[n-1].second << endl;
}