#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){
    if(v[i] % P == 0){
      if(v[i] > M) ret = 1;
    }else{
      ll x = 1;
      ll cnt = 0;
      while(x <= M){
        cnt++;
        x *= v[i];
      }
      ret = min(ret, cnt);
    }
  }

  if(ret == 1e18) cout << -1 << endl;
  else cout << ret << endl;
  
  return 0;
}