#include<bits/stdc++.h>
// #include<atcoder/all>

using namespace std;
// using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007

int main(){
  
  ll n,m,p;
  cin >> n >> m >> p;
  ll mx = 0;
  vector<ll> v(n);
  vector<ll> nv(n);
  rep(i,n){
    cin >> v[i];
    mx = max(mx,v[i]);
    while(v[i]%p == 0)v[i] /= p,nv[i]++;
  }
  ll res = MOD;
  rep(i,n){
    if(v[i] == 1)continue;
    ll k = mx;
    ll g = 1;
    while(k <= m)k *= v[i],g += nv[i]+1;
    res = min(res,g);
  }
  if(mx > m)res = 1;
  cout << (res != MOD ? res : -1) << "\n";


  return 0;
}