C++ :

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
int n, A, B, T;
int a[MAXN];

long long water(int &w, int W, int x) {
    long long cnt = ceil (1.0 * (x - w) / W);
    w += cnt * W - x;
    return x + cnt * T;
}

int main() {
    cin >> n >> A >> B >> T;
    for(int i = 1; i <= n; ++i) cin >> a[i];
    int l = 1, r = n, wl = A, wr = B;
    long long tl = 0, tr = 0;
    while(l <= r) {
        if(tl <= tr) tl += water(wl, A, a[l++]);
        else tr += water(wr, B, a[r--]);
    }
    cout << max(tl, tr);
    return 0;
}