#include<bits/stdc++.h>
#define int long long
using namespace std;

const int INF = 0x3f3f3f3f3f3f3f3f;

signed main() {
    int n, m, x, y; cin >> n >> m >> x >> y;
    vector<int> a(m + 1, 0);
    for (int i = 1; i <= m; i++) {
        cin >> a[i];
    }
    a.push_back(n + 1);
    vector<vector<int>> dp(m + 2, vector<int>(2, INF));
    dp[0][0] = 0;
    for (int i = 1; i <= m + 1; i++) {
        int d = a[i] - a[i - 1] - 1;
        int tmp = d % (y + 2);
        // y-x first
        if (tmp <= y - x) {
            dp[i][0] = min(dp[i][0], dp[i - 1][0] + d / (y + 2) * 2);
            dp[i][0] = min(dp[i][0], dp[i - 1][1] + d / (y + 2) * 2);
        }
        else if (tmp - y + x - 1 <= y - x) {
            dp[i][0] = min(dp[i][0], dp[i - 1][0] + d / (y + 2) * 2 + 1);
            dp[i][0] = min(dp[i][0], dp[i - 1][1] + d / (y + 2) * 2 + 1);
        }
        else {
            dp[i][1] = min(dp[i][1], dp[i - 1][0] + d / (y + 2) * 2 + 1);
            dp[i][1] = min(dp[i][1], dp[i - 1][1] + d / (y + 2) * 2 + 1);
        }
        // x first
        if (tmp <= x) {
            dp[i][1] = min(dp[i][1], dp[i - 1][0] + d / (y + 2) * 2);
        }
        else {
            dp[i][0] = min(dp[i][0], dp[i - 1][0] + d / (y + 2) * 2 + 1);
        }
    }
    cout << min(dp[m + 1][0], dp[m + 1][1]) << '\n';
}