#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m, p;
    cin >> n >> m >> p;
    vector<ll> a(n), b(n);
    for(int i = 0; i < n; ++i){
        cin >> a[i];
        b[i] = a[i];
        while(b[i] % p == 0)    b[i] /= p;
    }
    sort(rbegin(a), rend(a));
    sort(rbegin(b), rend(b));
    if(b[0] == 1 && a[0] <= m){
        cout << -1 << endl;
        return 0;
    }
    int ans = 0;
    ll prod = 1;
    while(prod <= m){
        ans += 1;
        if(prod * a[0] > m) prod *= a[0];
        else    prod *= b[0];
    }
    cout << ans << endl;

    return 0;
}