#include <bits/stdc++.h>

using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define FOR(i, n, m) for (int i = n; i < m; i++)
using ll = long long;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
void print() { std::cout << std::endl; }
template<class T, class... A> void print(const T& first, const A&... rest) { std::cout << first << " "; print(rest...); }
template<class... A> void print(const A&... rest) { print(rest...); }
# define SZ(x) ((int)(x).size())
const ll INF = 1LL<<60;

int main() {
    int n, m;
    ll a, b;
    cin >> n >> m >> a >> b;
    set<int> c;
    rep(i,m) {
        int x;
        cin >> x;
        c.insert(x);
    }
    vector<int> div;
    for (int x = 1; x * x <= n; x++) {
        if (x * x == n)div.emplace_back(x);
        else if (n % x == 0){
            div.emplace_back(x);
            div.emplace_back(n/x);
        }
    }
    sort(div.begin(), div.end());
    reverse(div.begin(), div.end());
    //cout << "ok" << endl;
    auto check = [&](int x, int y) -> bool {
        x -= y;
        if (x / y < m) {
            while (x >= y) {
                if (c.find(x) != c.end())return false;
                x -= y;
            }
            return true;
        }
        else {
            for(auto z:c) {
                if (z % y == 0 && z < x)return false;
            }
            return true;
        }
        
    };

    map<int, ll> memo;
    auto saiki = [&](auto&& saiki, int x) -> ll{
        if (x == 1)return 0;
        if (memo.find(x)!=memo.end())return memo[x];
        ll ans = INF;
        for(int y : div) {
            //print("x,y", x, y);
            if (y < x && x % y == 0 && check(x, y)) {
                ll d = x / y;
                d--;
                chmin(ans, saiki(saiki, y) + b + d * a);
            }
        }
        //cout << x << " " << ans << endl;
        memo[x] = ans;
        return ans;
    };
    if (n == 1)return 0;
    else {
        auto z = saiki(saiki, n);
        if (z == INF)cout << -1 << endl;
        else cout << z - b << endl;
    }

    
}