#include <bits/stdc++.h>
using namespace std;
void solve() {
    long long n, m, x, y;
    cin >> n >> m >> x >> y;
    x = x + 1, y = y + 2;
    vector<long long> p(m + 2);
    p[0] = 0;
    p[m + 1] = n + 1;
    for (int i = 1; i <= m; ++i)
        cin >> p[i];

    long long s = 0;
    long long a = -1;
    for (int i = 0; i <= m; ++i) {
        long long b = p[i];
        long long c = min(a + y, b + x);
        long long d = b + y;
        long long r = p[i + 1];
        a = b;

        if (c < r) {
            s += (r - c - 1) / y + 1;
            c += (r - c - 1) / y * y;
            a = max(a, c);
        }

        if (d < r) {
            s += (r - d - 1) / y + 1;
            d += (r - d - 1) / y * y;
            a = max(a, d);
        }
    }
    cout << s << endl;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    // cin >> T;
    while (T--) solve();
    return 0;
}