#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
// using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using pint = pair<lint, lint>;
using vp = vector<pint>;
vector<lint> divisor(lint n) {
	vector<lint> v;
	for (lint i = 1; i*i <= n; i++) {
		if (n % i == 0) {
			v.push_back(i);
			if (i*i != n) v.push_back(n/i);
		}
	}
	sort(v.begin(), v.end());
	return v;
}

int main() {
	lint N, M, A, B;
	cin >> N >> M >> A >> B;
	vi v(M);
	vin(v);

	lint a=0, b=LINF, c=1, x, y, z;
	sort(all(v));
	priority_queue<pint> q;
	map<pint, lint> m;
	set<pint> s;
	q.push({N, N});
	m[{N, N}] = -B;
	while (!q.empty()) {
		tie(x, y) = q.top();
		q.pop();
		if (s.count({x, y})) continue;
		s.insert({x, y});
		z = m[{x, y}];
		// list(x)
		// list(y)
		// show(z)
		if (x != y) {
			bool f = true;
			rep(i, M) {
				if (v[i] > x) break;
				if (v[i]%y == 0) f = false;
			}
			if (!f) continue;
			z += (x/y-1)*A;
			x = y;
			q.push({x, y});
			if (!m.count({x, y})) m[{x, y}] = z;
			else chmin(m[{x, y}], z);
		} else {
			vi w = divisor(x);
			rep(i, w.size()) {
				if (w[i] <= a) continue;
				if (s.count({x, w[i]})) continue;
				q.push({x, w[i]});
				m[{x, w[i]}] = z+B;
			}
		}
		// if (m.count({1, 1})) show((m[{1, 1}]))
	}
	if (!m.count({1, 1})) std::cout << -1 << '\n';
	else std::cout << m[{1, 1}] << '\n';
}