#include <bits/stdc++.h>
using namespace std;
const long long INF = 1100000000000000000;
int main(){
  int N, M, A, B;
  cin >> N >> M >> A >> B;
  vector<int> C(M);
  for (int i = 0; i < M; i++){
    cin >> C[i];
  }
  vector<int> F;
  for (int i = 1; i * i <= N; i++){
    if (N % i == 0){
      F.push_back(i);
      if (i * i < N){
        F.push_back(N / i);
      }
    }
  }
  sort(F.begin(), F.end());
  int cnt = F.size();
  vector<int> mn(cnt, N + 1);
  for (int i = 0; i < cnt; i++){
    for (int j = 0; j < M; j++){
      if (C[j] % F[i] == 0){
        mn[i] = min(mn[i], C[j]);
      }
    }
  }
  vector<long long> dp(cnt, INF);
  dp[0] = 0;
  for (int i = 0; i < cnt; i++){
    for (int j = i + 1; j < cnt; j++){
      if (F[j] % F[i] == 0 && F[j] < mn[i]){
        dp[j] = min(dp[j], dp[i] + (long long) (F[j] / F[i] - 1) * A + B);
      }
    }
  }
  if (dp[cnt - 1] == INF){
    cout << -1 << endl;
  } else {
    cout << dp[cnt - 1] - B << endl;
  }
}