#include <bits/stdc++.h>
using namespace std;
inline bool is_palindrome(const string& s) {
  return std::equal(s.begin(), s.end(), s.rbegin());
}
const long long MOD = 1000000007;
const long long INF = 1e9 + 5;
const double eps = 1e-7;
const double PI = acos(-1.0);
inline void debug_vi(vector<int> a) {
  for (long long i = (long long)(0); i < (long long)(a.size()); i++)
    cout << a[i] << " ";
}
inline void debug_vll(vector<long long> a) {
  for (long long i = (long long)(0); i < (long long)(a.size()); i++)
    cout << a[i] << " ";
}
const int N = 1e5 + 5;
int arr[N];
pair<int, int> xpos, ypos;
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, l, x, y, j;
  cin >> n >> l >> x >> y;
  xpos = {-1, -1};
  ypos = xpos;
  for (long long i = (long long)(0); i < (long long)(n); i++) {
    cin >> arr[i];
  }
  j = 0;
  for (long long i = (long long)(0); i < (long long)(n); i++) {
    while (j < n && arr[j] - arr[i] < x) j++;
    if (j < n && arr[j] - arr[i] == x) {
      xpos = {i, j};
      break;
    }
  }
  j = 0;
  for (long long i = (long long)(0); i < (long long)(n); i++) {
    while (j < n && arr[j] - arr[i] < y) j++;
    if (j < n && arr[j] - arr[i] == y) {
      ypos = {i, j};
      break;
    }
  }
  if (xpos.first != -1 && ypos.first != -1) {
    cout << 0;
  } else if (xpos.first != -1 || ypos.first != -1) {
    cout << 1 << "\n";
    if (xpos.first != -1) {
      cout << y;
    } else {
      cout << x;
    }
  } else {
    j = 0;
    for (long long i = (long long)(0); i < (long long)(n); i++) {
      while (j < n && arr[j] - arr[i] < x + y) j++;
      if (j < n && arr[j] - arr[i] == x + y) {
        cout << 1 << "\n";
        cout << arr[i] + x << "\n";
        return 0;
      }
    }
    j = 0;
    for (long long i = (long long)(0); i < (long long)(n); i++) {
      while (j < n && arr[j] - arr[i] < y - x) j++;
      if (j < n && arr[j] - arr[i] == y - x) {
        if (arr[i] - x >= 0) {
          cout << 1 << "\n";
          cout << arr[i] - x;
          return 0;
        } else if (arr[j] + x <= l) {
          cout << 1 << "\n";
          cout << arr[j] + x;
          return 0;
        }
      }
    }
    cout << 2 << "\n";
    cout << x << " " << y;
  }
  return 0;
}
