#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, M, P;
  cin >> N >> M >> P;
  vector<int> A(N);
  for(int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<vector<int>> p(31);
  bool ok = false;
  for (int i = 0; i < N; i++){
    int t = 0;
    int tmp = A[i];
    while (tmp % P == 0){
      tmp /= P;
      t++;
    }
    if (tmp > 1){
      ok = true;
    }
    p[t].push_back(A[i]);
  }
  if (!ok){
    cout << -1 << endl;
  } else {
    for (int i = 0; i < 31; i++){
      sort(p[i].begin(), p[i].end(), greater<int>());
    }
    vector<int> B;
    for (int i = 0; i < 31; i++){
      if (!p[i].empty()){
        B.push_back(p[i][0]);
      }
    }
    int cnt = B.size();
    map<long long, int> mp;
    queue<long long> Q;
    Q.push(1);
    mp[1] = 0;
    int ans;
    while (!Q.empty()){
      long long v = Q.front();
      Q.pop();
      if (v > M){
        ans = mp[v];
        break;
      }
      if (v % P == 0){
        if (!mp.count(v / P)){
          mp[v / P] = mp[v] + 1;
          Q.push(v / P);
        }
      } else {
        for (int i = 0; i < cnt; i++){
          if (!mp.count(v * B[i])){
            mp[v * B[i]] = mp[v] + 1;
            Q.push(v * B[i]);
          }
        }
      }
    }
    cout << ans << endl;
  }
}