#include <bits/stdc++.h>
using namespace std;
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define rep(i, n) repl(i, 0, n)
#define CST(x) cout << fixed << setprecision(x)
using ll = long long;
constexpr ll MOD = 1000000007;
constexpr int inf = 1e9 + 10;
constexpr ll INF = (ll)4e18 + 10;
constexpr int dx[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
constexpr int dy[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0};
template <class T>
inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);

    int n;
    ll m, p;
    cin >> n >> m >> p;
    ll a[n];
    ll mx = 0;
    vector<int> cnt(n);
    rep(i, n) {
        cin >> a[i];
        chmax(mx, a[i]);
        while (a[i] % p == 0) {
            cnt[i]++;
            a[i] /= p;
        }
    }

    ll M = 0, C = 0;
    rep(i, n) if (chmax(M, a[i])) C = cnt[i];

    if (M == 1) {
        if (mx > m)
            puts("1");
        else
            puts("-1");
        return 0;
    }

    ll now = 1, ans = 0;
    while (now <= m / mx) {
        now *= M;
        ans += C + 1;
    }

    cout << ans + 1 << endl;

    return 0;
}