/**
 * @file qoj6372-1.cpp
 * @author n685
 * @brief
 * @date 2024-02-23
 *
 *
 */
#include <bits/stdc++.h>

#ifdef LOCAL
#include "dd/debug.h"
#else
#define dbg(...) 42
#define dbgR(...) 4242
#define dbgP(...) 420
#define dbgRP(...) 420420
void nline() {}
#endif

const int MX = 201;
int n, d;
int64_t a, b;
std::bitset<MX + 50> p;

void small() {
  // std::array<std::vector<int64_t>, MX> dp;
  std::array<std::vector<int64_t>, 2> dp;
  dp.fill(std::vector<int64_t>(1 << d, (int64_t)4e18));
  int par = 0;
  for (int i = 0; i < (1 << d); ++i) {
    int64_t val = 0;
    for (int j = 0; j < d - 1; ++j) {
      if ((i & (2 << j))) {
        if (i & (1 << j)) {
          val += b;
        } else {
          val += a;
        }
      }
    }
    dp[par][i] = val;
  }
  for (int i = d; i < MX; ++i) {
    par = !par;
    for (int j = 0; j < (1 << d); ++j) {
      dp[par][j] = (int64_t)4e18;
      auto apply = [&](int k) {
        int64_t val = dp[!par][k];
        if (k % 2) {
          if (j % 2) {
            val += b;
          } else {
            val += a;
          }
        }
        dp[par][j] = std::min(dp[par][j], val);
      };
      int k = j / 2;
      if ((j % 2) || !p[i - d]) {
        apply(k);
      }
      k += (1 << (d - 1));
      apply(k);
    }
  }
  int64_t ans = (int64_t)4e18;
  for (int i = 0; i < (1 << d); ++i) {
    if (i % 2) {
      dp[par][i] += a;
    }
    ans = std::min(ans, dp[par][i]);
  }
  std::cout << ans << '\n';
}
void big() {
  int m = (MX + d - 1) / d;
  int sz = m * d;
  int64_t ans = (int64_t)4e18;
  for (int i = 0; i < (1 << m); ++i) {
    bool g = true;
    for (int j = 0; j < m - 1; ++j) {
      if (p[d * j] && !(i & (1 << (m - 2 - j)) && !(i & (1 << (m - 1 - j))))) {
        g = false;
        break;
      }
    }
    if (!g) {
      continue;
    }
    std::array<std::vector<int64_t>, 2> dp;
    dp.fill(std::vector<int64_t>(1 << m, (int64_t)4e18));
    dp[0][i] = 0;
    int par = 1;
    for (int j = 1; j < d; ++j) {
      for (int k = 0; k < m; ++k) {
        for (int l = 0; l < (1 << m); ++l) {
          dp[par][l] = (int64_t)4e18;
          int loc = k * d + j;
          if (k > 0 && p[loc - d] && !(l & 1) && !(l & 2)) {
            continue;
          }
          dp[par][l] =
              std::min(dp[!par][l / 2],
                       dp[!par][l / 2 + (1 << (m - 1))] + ((l % 2) ? b : a));
        }
        par = !par;
      }
    }
    par = !par;
    for (int j = 0; j < (1 << m); ++j) {
      for (int k = 0; k < m - 1; ++k) {
        if (j & (2 << k)) {
          if (i & (1 << k)) {
            dp[par][j] += b;
          } else {
            dp[par][j] += a;
          }
        }
      }
      ans = std::min(ans, dp[par][j]);
    }
  }
  std::cout << ans << '\n';
}

int main() {
#ifndef LOCAL
  std::cin.tie(nullptr)->sync_with_stdio(false);
#endif

  std::cin >> n >> d >> a >> b;
  if (a < b) {
    b = a;
  }

  for (int i = 0; i < n; ++i) {
    int x;
    std::cin >> x;
    --x;
    p[x] = 1;
  }

  d *= 2;
  if (d <= 20) {
    small();
  } else {
    big();
  }
}