#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>;

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;
    int mx_index = -1;
    rep(i, 0, n){
        if(mx < a[i]%p){
            mx = a[i]%p;
            mx_index = i;
        }
    }
    if(a[n-1] > m){
        cout << 0 << endl;
        return 0;
    }
    if(mx <= 0){
        cout << -1 << endl;
        return 0;
    }
    ll x = 1;
    while(x <= m){
        cnt++;
        if(x*a[n-1] > m) break;
        else if(x%p == 0) x /= p;
        else x *= a[mx_index];
    }
    cout << cnt << endl;
    return 0;
}