#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

deque<pll> deq;
ll N, A, B, W;
bool check(pll f1, pll f2, pll f3){
    return (f2.fi-f1.fi)*(f3.se-f2.se) >= (f2.se-f1.se)*(f3.fi-f2.fi);
}

void add(pll conf2){
    while((ll)deq.size()>=2){
        pll conf1 = deq.back();
        deq.pop_back();
        pll conf0 = deq.back();
        if(!check(conf0, conf1, conf2)){
            deq.push_back(conf1);
            break;
        }
    }
    deq.push_back(conf2);
}

ll f(pll coef, ll x){ return (coef.fi*x + coef.se);}

ll query(ll x){
    while((ll)deq.size()>=2){
        pll coef0 = deq.front();
        deq.pop_front();
        pll coef1 = deq.front();
        deq.pop_front();
        if(f(coef0, x) >= f(coef1, x)){
            deq.push_front(coef1);
        }else{
            deq.push_front(coef1);
            deq.push_front(coef0);
            break;
        }
    }

    return f(deq.front(), x);
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    cin >> N >> A >> B >> W;
    vector<ll> D(N+1);
    for(ll i=1; i<=N; i++) cin >> D[i];

    vector<ll> dp(N+1);
    dp[0] = W;
    add({B-2*A, 2*W});
    for(ll i=1; i<=N; i++){
        add({B-2*B*i-2*A, B*i*i-B*i+2*A*i+2*dp[i-1]+2*D[i]});
        dp[i] = (B*i*i+query(i))/2;
    }

    cout << dp[N] << endl;
}