#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  ll N, M, P;
  cin >> N >> M >> P;
  vector<ll> v(N);
  rep(i,N){
    cin >> v[i];
  }

  ll ret = 1e18;
  rep(i,N){
    ll x = 1;
    map<ll,bool> used;
    ll cnt = 0;
    while(x <= M){
      cnt++;
      if(x%P==0){
        x /= P;
        while(x%P==0){
          x /= P;
          cnt++;
        }
      }
      else x *= v[i];
      
      if(used.count(x) > 0){
        x = -1;
        break;
      }
      used[x] = true;
    }
    
    if(x > M){
      ret = min(ret, cnt);
    }
  }
  
  if(ret == 1e18) cout << -1 << endl;
  else cout << ret << endl;
  
  return 0;
}