#include <bits/stdc++.h>

using namespace std;

#define REP(i, n) for(int i=0; i<(n); ++i)
#define RREP(i, n) for(int i=(n);i>=0;--i)
#define FOR(i, a, n) for (int i=(a); i<(n); ++i)
#define RFOR(i, a, b) for(int i=(a);i>=(b);--i)


#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(),(x).end()

#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl
#define DEBUG(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<<endl;

template<class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  REP(i, SZ(v)) {
    if (i) os << " ";
    os << v[i];
  }
  return os;
}

template <class T>
void debug(const vector<T> &v) {
  cout << "[";
  REP(i, SZ(v)) {
    if(i) cout << ", ";
    cout << v[i];
  }
  cout << "]" << endl;
}

template<class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << p.first << " " << p.second;
}

template <class T, class U>
void debug(const pair<T, U> &p) {
  cout << "(" << p.first << " " << p.second << ")" << endl;
}

template<class T>
bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template<class T>
bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vi>;
using vvll = vector<vll>;

const ll MOD = 1e9 + 7;
const ll MOD998 = 998244353;
const int INF = INT_MAX;
const ll LINF = LLONG_MAX;
const int inf = INT_MIN;
const ll linf = LLONG_MIN;
const ld eps = 1e-9;


template<int m>
struct mint {
  int x;

  mint(ll x = 0) : x(((x % m) + m) % m) {}

  mint operator-() const { return x ? m - x : 0; }

  mint &operator+=(mint r) {
    if ((x += r.x) >= m) x -= m;
    return *this;
  }

  mint &operator-=(mint r) {
    if ((x -= r.x) < 0) x += m;
    return *this;
  }

  mint &operator*=(mint r) {
    x = ((ll) x * r.x) % m;
    return *this;
  }

  mint inv() const { return pow(m - 2); }

  mint &operator/=(mint r) { return *this *= r.inv(); }

  friend mint operator+(mint l, mint r) { return l += r; }

  friend mint operator-(mint l, mint r) { return l -= r; }

  friend mint operator*(mint l, mint r) { return l *= r; }

  friend mint operator/(mint l, mint r) { return l /= r; }

  mint pow(ll n) const {
    mint ret = 1, tmp = *this;
    while (n) {
      if (n & 1) ret *= tmp;
      tmp *= tmp, n >>= 1;
    }
    return ret;
  }

  friend bool operator==(mint l, mint r) { return l.x == r.x; }

  friend bool operator!=(mint l, mint r) { return l.x != r.x; }

  friend ostream &operator<<(ostream &os, mint a) {
    return os << a.x;
  }

  friend istream &operator>>(istream &is, mint &a) {
    ll x;
    is >> x;
    a = x;
    return is;
  }
};

using Int = mint<MOD>;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  int n, m, p; cin >> n >> m >> p;
  vector<pair<ll, ll>> v;
  int ma = 0;
  REP(i, n) {
    int a; cin >> a;
    chmax(ma, a);
    int cnt = 1;
    while(a % p == 0) {
      a /= p;
      cnt++;
    }
    v.emplace_back(a, cnt);
  }

  if(m == 1) {
    cout << 0 << endl;
    return 0;
  }

  int ans = INF;
  if(ma >= m) ans = 1;
  REP(i, n) {
    ll now = 1;
    int cnt = 1;
    if(v[i].first == 1) continue;
    while(now * ma < m) {
      now *= v[i].first;
      cnt += v[i].second;
    }
    chmin(ans, cnt);
  }
  cout << (ans == INF ? -1 : ans) << endl;

  return 0;
}