#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

template<class T>
vector<T> divisors(T x) {
  vector<T> res1, res2;
  T d = 1;
  for(; d * d < x; d++) {
    if (x % d == 0) {
      res1.emplace_back(d);
      res2.emplace_back(x / d);
    }
  }
  if (d * d == x) res1.emplace_back(d);
  res1.insert(res1.end(), res2.rbegin(), res2.rend());
  return res1;
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m, a, b;
  constexpr long long INF = 8002003004005006007;
  ll ans = INF;
  cin >> n >> m >> a >> b;
  VI c(m);
  rep(i, m) cin >> c[i];
  sort(all(c));
  VI divs = divisors(n);
  const int sz = divs.size();
  VL dp(sz, INF);
  dp[sz - 1] = 0;
  rrep(i, sz) if (dp[i] != INF) {
    int rest = divs[i];
    int scale = n / rest;
    VI ds = divisors(rest);
    int dsz = ds.size();
    int ptr = 0;
    int dp_i = sz - 1;
    for(int j = 1; j < dsz; j++) {
      bool ok = true;
      while(ptr < m && c[ptr] <= ds[j] * scale) {
        if (c[ptr] % scale == 0) {
          ok = false;
          break;
        }
        ptr++;
      }
      if (!ok) break;
      ll c = dp[i] + ll(ds[j] - 1) * a;
      if (j == dsz - 1) chmin(ans, c);
      else {
        while(divs[dp_i] != rest / ds[j]) dp_i--;
        chmin(dp[dp_i], c + b);
      }
    }
  }
  if (ans == INF) ans = -1;
  cout << ans << '\n';
}