#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    ll n, m, p; cin >> n >> m >> p;
    vector<ll> a(n);
    vector<ll> b(n);
    vector<ll> cnt(n);
    ll a_max = 0, b_max = 0;
    for(int i = 0; i < n; i++) {
        cin >> a[i];
        b[i] = a[i];
        while(b[i]%p == 0) {
            b[i] /= p;
            cnt[i]++;
        }
        chmax(a_max, a[i]);
        chmax(b_max, b[i]);
    }
    if(b_max == 1){
        if(m > a_max){
            cout << -1 << endl;
            return 0;
        }else{
            cout << 1 << endl;
            return 0;
        }
    }
    if(a_max > m){
        cout << 1 << endl;
        return 0;
    }
    int ans = 1e9;
    for(int i = 0; i < n; i++){
        ll tmp = 1;
        int s = 0;
        if(b[i] == 1) continue;
        while(tmp <= m){
            if(tmp*a_max > m) tmp *= a_max;
            else{
                tmp *= b[i];
                s += cnt[i];
            }
            s++;
        }
        chmin(ans, s);
    }
    
    cout << ans << endl;
}