#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define rrep2(ri,x,n) for(int ri = (int)(n-1); ri >= (int)(x); ri--)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

pair<ll, ll> fc(int a, int p){
  int res = 1;
  while(a % p == 0){
    res++;
    a /= p;
  }
  return {a, res};
}

int main(){
  int n, m, p;
  cin >> n >> m >> p;
  if(m == 1){
    cout << 0 << endl;
    return 0;
  }
  ll now = 1;
  vector<pair<int, int>> ab;
  rep(i, n){
    int in;
    cin >> in;
    now = max((int)now, in);
    auto [a, b] = fc(in, p);
    if(a != 1){
      ab.push_back({a, b});
    }
  }
  int ans = 1001001001;
  if(now <= m){
    for(auto [a, b] : ab){
      ll nw = now;
      int add = 1;
      while(nw <= m){
        nw *= a;
        add += b;
      }
      ans = min(ans, add);
    }
  }
  if(ab.size() == 0) ans = -1;
  cout << ans << endl;
  return 0;
}