#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (long long i = 0; i < (n); ++i)
using ll = long long;
using P = pair<ll,ll>;
using PP = pair<P,ll>;
using vec = vector<ll>;
using vecp = vector<P>;
using mat = vector<vec>;
using matp = vector<vecp>;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define all(v) v.begin(), v.end()




int main(){
  ll N,M,P,m=0;
  cin >> N >> M >> P;
  vec A(N),B(30,0);
  rep(i,N){
    cin >> A.at(i);
    m=max(m,A.at(i));
    ll t=0;
    while(A.at(i)%P==0){
      t++;
      A.at(i)/=P;
    }
    B.at(t)=max(B.at(t),A.at(i));
  }
  if(m>M){
    cout << 1 << endl;
    return 0;
  }
  rep(i,30){
    if(B.at(i)>1){
      break;
    }
    if(i==29){
      cout << -1 << endl;
      return 0;
    }
  }
  vec dp(900,0);
  dp.at(0)=1;
  rep(i,900){
    if(dp.at(i)*m>M){
      cout << i+1 << endl;
      return 0;
    }
    rep(j,30){
      dp.at(i+j+1)=max(dp.at(i+j+1),dp.at(i)*B.at(j));
    }
  }
  
}