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

#define rep(i,n) for (int i=0;i<(n);++i)
#define rep2(i,a,b) for (int i=(a);i<(b);++i)
#define rrep(i,n) for (int i=(n)-1;i>=0;--i)
#define rrep2(i,a,b) for (int i=(a)-1;i>=b;--i)
#define chmin(a,b) (a)=min((a),(b));
#define chmax(a,b) (a)=max((a),(b));
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define printV(_v) cout<<(#_v)<<":";for(auto(_x):(_v)){cout<<" "<<(_x);}cout<<endl;
#define printVS(vs) cout<<(#vs)<<":"<<endl;for(auto(s):(vs)){cout<<(s)<< endl;}
#define printVV(vv) cout<<(#vv)<<":"<<endl;for(auto(v):(vv)){for(auto(x):(v)){cout<<" "<<(x);}cout<<endl;}
#define printP(p) cout<<(#p)<<(p).first<<" "<<(p).second<<endl;
#define printVP(vp) cout<<(#vp)<<":"<<endl;for(auto(p):(vp)){cout<<(p).first<<" "<<(p).second<<endl;}

inline void output(){ cout << endl; }
template<typename First, typename... Rest>
inline void output(const First& first, const Rest&... rest) {
    cout << first << " "; output(rest...);
}

using ll = long long;
using Pii = pair<int, int>;
using TUPLE = tuple<int, int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
const int inf = 1ll << 60;
const int mod = 1e9 + 7;
using Graph = vector<vector<int>>;

int N, A, B, W;
int D[300010];
int deq[300010];
int dp[300010];

int a(int i) {
    return - i * B;
}

int b(int i) {
    return dp[i] + i * A + i * (i + 1) * B / 2;
}

int f(int i, int x) {
    return a(i) * x + b(i);
}

bool check(int f1, int f2, int f3) {
    int a1 = a(f1), b1 = b(f1);
    int a2 = a(f2), b2 = b(f2);
    int a3 = a(f3), b3 = b(f3);
    return (a2 - a1) * (b3 - b2) >= (b2 - b1) * (a3 - a2);
}

main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    cin >> N >> A >> B >> W;
    rep(i, N) cin >> D[i];

    int s = 0, t = 1;
    deq[0] = 0;
    dp[0] = W;
    rep2(i, 1, N + 1) {
        dp[i] = D[i - 1] - (i - 1) * A + i * (i - 1) * B / 2 + f(deq[s], i);
        while (s + 1 < t && check(deq[t - 2], deq[t - 1], i)) t--;
        deq[t++] = i;
        while (s + 1 < t && f(deq[s], i) >= f(deq[s + 1], i)) s++;
    }

    int ans = inf;
    rep(i, N + 1) {
        chmin(ans, dp[i] - (N - i) * A + (N - i) * (N - i + 1) * B / 2);
    }
    cout << ans << endl;
}