#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <forward_list>
#include <fstream>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <streambuf>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <valarray>
#include <vector>

using namespace std;

using ll = long long;
using cd = complex<double>;

constexpr ll mod = 1e9 + 7, maxn = 3e5 + 10;

ll lgput(ll x, ll y, ll r) { return y == 0 ? r : lgput(x * x % mod, y / 2, y % 2 ? x * r % mod : r); }

ll gcd(ll x, ll y) { return y == 0 ? x : gcd(y, x % y); }

pair<ll, ll> euclid_extins(ll x, ll y) {
    pair<ll, ll> tmp;
    return x == 0
               ? make_pair(0ll, 1ll)
               : (tmp = euclid_extins(y % x, x), swap(tmp.first, tmp.second), tmp.first -= tmp.second * (y / x), tmp);
}

ll inv_mod(ll x, ll mod) { return (euclid_extins(mod, x).second % mod + mod) % mod; }

int n, m, a, b;
vector<int> bad;

vector<long long> factors, dp;

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

    cin >> n >> m >> a >> b;

    bad.resize(m);
    for (auto& x : bad) cin >> x;

    for (int i = 1; i * i <= n; ++i)
        if (n % i == 0) {
            factors.push_back(i);
            factors.push_back(n / i);
        }
    sort(begin(factors), end(factors));
    factors.erase(unique(begin(factors), end(factors)), end(factors));

    dp.resize(factors.size(), (long long)1e9 * (long long)1e9 + 10);
    dp[0] = 0;

    for (int i = 0; i < factors.size(); ++i) {
        long long max_jmp = (ll)1e9 * (ll)1e9;
        for (auto b : bad)
            if (b % factors[i] == 0) max_jmp = min(max_jmp, (ll)b);

        for (int j = i + 1; j < factors.size(); ++j) {
            if (factors[j] >= max_jmp) break;
            if (factors[j] % factors[i]) continue;
            dp[j] = min(dp[j], dp[i] + (long long)a * (factors[j] / factors[i] - 1) + b);
        }
    }

    cout << (dp.back() > (ll)1e9 * (ll)1e9 ? -1 : dp.back() - b) << endl;
}