/* -*- coding: utf-8 -*-
 *
 * 2039.cc:  No.2039 Copy and Avoid - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_M = 5000;
const int MAX_K = 1344;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;

/* global variables */

int cs[MAX_M], ds[MAX_K];
ll dp[MAX_K];

/* subroutines */

inline void setmin(ll &a, ll b) { if (a > b) a = b; }

/* main */

int main() {
  int n, m, a, b;
  scanf("%d%d%d%d", &n, &m, &a, &b);
  for (int i = 0; i < m; i++) scanf("%d", cs + i);
  sort(cs, cs + m);

  int k = 0;
  for (int p = 1; p * p <= n; p++)
    if (n % p == 0) {
      ds[k++] = p;
      int q = n / p;
      if (q != p) ds[k++] = q;
    }
  sort(ds, ds + k);
  //for (int i = 0; i < k; i++) printf("%d ", ds[i]); putchar('\n');

  fill(dp, dp + k, LINF);
  dp[0] = 0;

  for (int i = 0; i < k; i++) {
    if (dp[i] >= LINF) continue;

    int di = ds[i];
    int x = lower_bound(cs, cs + m, di) - cs;
    for (; x < m && cs[x] % di != 0; x++);
    int maxj = (x >= m) ? k : lower_bound(ds, ds + k, cs[x]) - ds;
    //printf("ds[%d]=%d, maxj=%d\n", i, di, maxj);

    for (int j = i + 1; j < maxj; j++)
      setmin(dp[j], dp[i] + ((ll)a * (ds[j] / di - 1) + b));
  }

  printf("%lld\n", (dp[k - 1] < LINF) ? dp[k - 1] - b : -1LL);
  return 0;
}