#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
const int MOD = 1000000007;
//const int MOD = 998244353;
const double PI = 3.14159265358979323846;

int main(){
    ll n,m,p;
    cin >> n >> m >> p;
    vector<ll> a(n);
    vector<ll> b(n);
    vector<ll> cnt(n,1);
    ll mx = 0;
    int mx_idx = -1;
    bool ok = false;
    rep(i,n){
        cin >> a[i];
        if(mx < a[i]){
            mx = a[i];
            mx_idx = i;
        }
        b[i] = a[i];
        while(b[i]%p==0){
            b[i] /= p;
            ++cnt[i];
        }
        if(b[i]!=1) ok = true;
    }
    if(!ok && mx <= m){
        cout << -1 << endl;
        return 0;
    }
    ll ans = INF;
    rep(i,n){
        if(b[i]==1) continue;
        ll x = 1;
        ll res = 0;
        while(x <= m){
            if(x*a[i] > m){
                x *= a[i];
                res ++;
            }else{
                x *= b[i];
                res += cnt[i];
            }
        }
        ans = min(ans,res);
        res = 1;
        x = mx;
        while(x <= m){
            x *= b[i];
            res += cnt[i];
        }
        ans = min(ans,res);
    }
    cout << ans << endl;

    return 0;
}