#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


/*
  z[x] \in {0, 1}
  
  z[X[i]] = 1  or  z[X[i] + D] = 1
  z[x-1] = 0 && z[x] = 1: cost += A
  z[x-1] = 1 && z[x] = 1: cost += B
  
  x -> (x/D, x%D)
*/

constexpr int INF = 1001001001;

int N, D, A, B;
vector<int> X;

int C;
vector<int> on;


namespace rowmajor {
int run() {
  vector<int> crt(1 << D, INF);
  crt[0] = 0;
  for (int x = X[0]; x <= X[N - 1] + D; ++x) {
    const int d = x % D;
    const int d1 = d ? (d - 1) : (D - 1);
    vector<int> nxt(1 << D, INF);
    for (int p = 0; p < 1 << D; ++p) if (crt[p] < INF) {
      // 0
      if (!on[x] || (p & 1 << d)) {
        chmin(nxt[p & ~(1 << d)], crt[p]);
      }
      // 1
      chmin(nxt[p | 1 << d], crt[p] + ((p & 1 << d1) ? B : A));
    }
    crt.swap(nxt);
  }
  const int ans = *min_element(crt.begin(), crt.end());
  return ans;
}
}  // rowmajor


namespace colmajor {
int run() {
  int ans = INF;
  // fix first column
  for (int p0 = 0; p0 < 1 << C; p0 += 2) {
    bool ok = true;
    for (int c = 1; c < C; ++c) if (on[c * D]) {
      ok = ok && ((p0 & 1 << (c-1)) || (p0 & 1 << c));
    }
    if (ok) {
      vector<int> crt(1 << C, INF);
      crt[p0] = 0;
      for (int d = 1; d < D; ++d) for (int c = 0; c < C; ++c) {
        const int x = c * D + d;
        vector<int> nxt(1 << C, INF);
        for (int p = 0; p < 1 << C; ++p) if (crt[p] < INF) {
          // 0
          if (!on[x] || (p & 1 << (c-1))) {
            chmin(nxt[p & ~(1 << c)], crt[p]);
          }
          // 1
          chmin(nxt[p | 1 << c], crt[p] + ((p & 1 << c) ? B : A));
        }
        crt.swap(nxt);
      }
      for (int p = 0; p < 1 << C; ++p) if (crt[p] < INF) {
        int cost = crt[p];
        for (int c = 1; c < C; ++c) if (p0 & 1 << c) {
          cost += ((p & 1 << (c-1)) ? B : A);
        }
// cerr<<"p0 = "<<p0<<", p = "<<p<<": cost = "<<cost<<endl;
        chmin(ans, cost);
      }
    }
  }
  return ans;
}
}  // colmajor


int main() {
  for (; ~scanf("%d%d%d%d", &N, &D, &A, &B); ) {
    D *= 2;
    chmin(B, A);
    X.resize(N);
    for (int i = 0; i < N; ++i) {
      scanf("%d", &X[i]);
    }
    sort(X.begin(), X.end());
    
    C = (X[N - 1] + D) / D + 1;
    on.assign(C * D, 0);
    for (int i = 0; i < N; ++i) {
      on[X[i] + D] = 1;
    }
    
    int ans;
    if (D <= 2 * C) {
      ans = rowmajor::run();
    } else {
      ans = colmajor::run();
    }
    printf("%d\n", ans);
  }
  return 0;
}