#include <bits/stdc++.h>
#include <atcoder/all>
typedef long long int ll;
using namespace std;
typedef pair<ll, ll> P;
using namespace atcoder;
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
#define USE998244353
#ifdef USE998244353
const ll MOD = 998244353;
using mint = modint998244353;
#else
const ll MOD = 1000000007;
using mint = modint1000000007;
#endif
const int MAX = 2000005;
long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll gcd(ll x, ll y) {
   if (y == 0) return x;
   else if (y > x) {
       return gcd (y, x); 
   }
   else return gcd(x % y, y);
}
ll lcm(ll x, ll y) {
   return x / gcd(x, y) * y;
}
ll my_sqrt(ll x) {
    // 
    ll m = 0;
    ll M = 3000000001;
    while (M - m > 1) {
        ll now = (M + m) / 2;
        if (now * now <= x) {
            m = now;
        }
        else {
            M = now;
        }
    }
    return m;
}
ll keta(ll num, ll arity) {
    ll ret = 0;
    while (num) {
        num /= arity;
        ret++;
    }
    return ret;
}
ll ceil(ll n, ll m) {
    // n > 0, m > 0
    ll ret = n / m;
    if (n % m) ret++;
    return ret;
}
ll pow_ll(ll x, ll n) {
    if (n == 0) return 1;
    if (n % 2) {
        return pow_ll(x, n - 1) * x;
    }
    else {
        ll tmp = pow_ll(x, n / 2);
        return tmp * tmp;
    }
}
vector<ll> compress(vector<ll>& v) {
    // [3 5 5 6 1 1 10 1] -> [1 2 2 3 0 0 4 0] 
    vector<ll> u = v;
    sort(u.begin(), u.end());
    u.erase(unique(u.begin(),u.end()),u.end());
    map<ll, ll> mp;
    for (int i = 0; i < u.size(); i++) {
        mp[u[i]] = i;
    }
    for (int i = 0; i < v.size(); i++) {
        v[i] = mp[v[i]];
    }
    return v;
}

int main() {
    int n;
    cin >> n;
    ll m, p;
    cin >> m >> p;
    vector<ll> a(n);
    vector<int> opNum(n, 1);
    bool infinite = true;
    vector<ll> multiplyMax(30, 1); // in cost of i, how maxmize the ratio
    ll finisher = 1;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        finisher = max(finisher, a[i]);
        while (a[i] % p == 0) {
            opNum[i]++;
            a[i] /= p;
        }
        if (a[i] > 1) infinite = false;
    }
    if (infinite) {
        if (finisher > m) {
            cout << 1 << endl;
        }
        else {
            cout << -1 << endl;
        }
        return 0;
    }

    for (int i = 0; i < n; i++) {
        for (int j = 1; j < 30; j++) {
            if (opNum[i] <= j) {
                multiplyMax[j] = max(multiplyMax[j], a[i]);
            }
        }
    }
    // for (int j = 1; j < 30; j++) {
    //     cout << j << ' ' << multiplyMax[j] << endl;
    // }
    min_priority_queue<pair<int, ll>> que;
    que.push({0, -1});
    vector<bool> checked(30, false);
    while (true) {
        int opNum = que.top().first;
        ll value = -que.top().second;
        // cout << "hi " << opNum << ' ' << value << endl;
        if (value > m) {
            cout << opNum << endl;
            return 0;
        }
        if (value * finisher > m) {
            cout << opNum + 1 << endl;
            return 0;
        }
        que.pop();
        if (checked[opNum]) continue;
        checked[opNum] = true;
        for (int i = 1; i < 30; i++) {
            que.push({opNum + i, -value * multiplyMax[i]});
        }
    }
    return 0;
}