#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <cassert>
#include <numeric>
#include <functional>
#include <ctime>
#include <bitset>
#pragma warning(disable:4996) 

//#define ATCODER
#ifdef ATCODER
#include <atcoder/all>
#endif

typedef long long ll;
typedef unsigned long long ull;
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define LINF3 1000000000000
#define INF 2140000000
//const long long MOD = 1000000007;
const long long MOD = 998244353;

using namespace std;
#ifdef ATCODER
using namespace atcoder;
#endif

typedef pair<ll, int> P;
vector<ll> dijkstra(int s, const vector<vector<pair<int, ll> > >& G) {
    priority_queue< P, vector<P>, greater<P> > que;
    vector<ll> d(G.size(), LINF);
    d[s] = 0;
    que.push(P(0, s));
    while (!que.empty()) {
        ll curr = que.top().second;
        ll  dcurr = que.top().first;
        que.pop();
        if (d[curr] < dcurr) continue;
        int i;
        for (i = 0; i < (int)G[curr].size(); i++) {
            int next = G[curr][i].first;
            ll  dist = G[curr][i].second;
            if (d[next] > d[curr] + dist) {
                d[next] = d[curr] + dist;
                que.push(P(d[next], next));
            }
        }
    }
    return d;
}

void solve()
{
    int n, m, a, b;
    scanf("%d%d%d%d", &n,&m,&a,&b);
    vector<int> c(m);
    for (int i = 0; i < m; i++) {
        scanf("%d", &c[i]);
    }

    vector<int> v0;
    for (int i = 1; i <= 100000; i++) {
        if (n%i == 0) {
            if (n / i < i) {
                break;
            }
            else {
                v0.push_back(i);
                if (n / i > i) {
                    v0.push_back(n/i);
                }
            }
        }
    }
    sort(v0.begin(), v0.end());

    int num = (int)v0.size();
    vector<int> lim(num, INF);
    for (int i = 0; i < num; i++) {
        for (int k = 0; k < m; k++) {
            if (c[k] % v0[i] == 0) {
                int tmp = c[k] / v0[i];
                lim[i] = min(lim[i], tmp);
            }
        }
    }

    vector<vector<pair<int, ll>>> g(num);
    for (int i = 0; i < num; i++) {
        for (int j = i + 1; j < num; j++) {
            if (v0[j] % v0[i] == 0) {
                int tmp = v0[j] / v0[i];
                if (lim[i] <= tmp) continue;
                ll cost = (ll)a * (tmp-1) + b;
                g[i].push_back(make_pair(j, cost));
            }
        }
    }

    vector<ll> dist = dijkstra(0, g);

    ll ans = LINF;
    for (int i = 0; i < num; i++) {
        if (dist[i] < LINF) {
            int tmp = n / v0[i];
            if (lim[i] <= tmp) continue;
            ll ans0 = dist[i] + (n / v0[i] - 1) * (ll)a;
            ans = min(ans, ans0);
        }
    }
    if (ans == LINF) {
        printf("-1\n");
    }
    else {
        printf("%lld\n", ans);
    }
    return;
}

int main()
{
#if 1
    solve();
#else
    int T, t;
    scanf("%d", &T);
    for (t = 0; t < T; t++) {
        //printf("Case #%d: ", t + 1);
        solve();
    }
#endif
    return 0;
}