#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<int> a(n), b(n), divcnt(n);
    int amax = 0;
    for(int i = 0; i < n; ++i){
        cin >> a[i];
        chmax(amax, a[i]);
        b[i] = a[i];
        while(b[i] % p == 0){
            b[i] /= p;
            divcnt[i] += 1;
        }
    }

    int ans = INF;
    for(int i = 0; i < n; ++i){
        if(a[i] > m){
            cout << 1 << endl;
            return 0;
        }
        if(b[i] == 1)   continue;
        ll prod = 1;
        int sum = 0;
        while(prod <= m){
            sum += 1;
            if(prod * amax > m){
                prod *= amax;
            }
            else if(prod * a[i] > m){
                prod *= a[i];
            }
            else{
                prod *= b[i];
                sum += divcnt[i];
            }
        }
        chmin(ans, sum);
    }
    
    if(ans == INF)  ans = -1;
    cout << ans << endl;

    return 0;
}