#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef __int128 INT;


/*cin高速化*/
struct INIT{INIT(){ios::sync_with_stdio(false);cin.tie(0);}}init;

ostream& operator<<(ostream &os,INT x){
    LL y;
    y=x;
    assert((y>=0&&x>=0) || (y<0&&x<0));
    os << y;
    return os;
}
istream& operator>>(istream &is,INT& x){
    LL y;
    is >> y;
    x = y;
    return is;
}

const INT INF = 1e24;


namespace CHT{
    using TYPE=INT;
#define A first
#define B second
#define SIZE 1000000
    pair<TYPE,TYPE> mem[SIZE];
    template<typename T>
    inline bool is_minimam(T a1,T b1,T a2,T b2,T a3,T b3){return (a2-a1)*(b3-b2)>=(b2-b1)*(a3-a2);}
    template<typename T>
    inline bool is_maximam(T a1,T b1,T a2,T b2,T a3,T b3){return is_minimam(-a1,-b1,-a2,-b2,-a3,-b3);}
    template<typename T>
    inline bool check(pair<T,T> L1,pair<T,T> L2,pair<T,T> L3){
        return is_minimam(L1.A,L1.B,L2.A,L2.B,L3.A,L3.B);
    }
    template<typename T>
    inline T calc(pair<T,T> L,T now){
        return L.A*now+L.B;
    }
};
template<typename T>
ostream& operator<<(ostream& os,pair<T,T> t){
    os <<"("<< t.first << " "<<t.second << ")";
    return os;
}
#define mp(a,b) std::make_pair(a,b)
template<typename T>
class convex_hull_trick{
    pair<T,T> *deque;
    int s,t;
public:
    convex_hull_trick(pair<T,T> *mem):deque(mem),s(0),t(0){}
    convex_hull_trick():convex_hull_trick(CHT::mem){}
    void add(T a,T b){
        auto L=mp(a,b);
        while(s+1<t&&CHT::check(deque[t-2],deque[t-1],L))t--;
        deque[t++]=L;
    }
    T get(T now){
        while(s+1<t&&CHT::calc(deque[s],now)>=CHT::calc(deque[s+1],now))s++;
        return CHT::calc(deque[s],now);
    }
};


int main() {
    INT N,A,B,W;
    /*input N,A,B,W*/
    {
        cin >> N >> A >> B >> W;
        assert(1 <= N && N <= 300000);
        assert(0 <= A && A <= 1000000);
        assert(0 <= B && B <= 1000000);
        assert(0 <= W && W <= 1000000);
    }
    vector<INT> D(N);
    {
        for(auto& it : D){
            cin >> it;
            assert(0 <= it && it <= 1000000);
        }
    }


    /*DP*/
    convex_hull_trick<INT> deq;
    vector<INT> dp(N+1,INF);
    dp[0] = W;
    deq.add( - 0 * B,dp[0] + 0 * A + B * 0 * (0 - 1) / 2);
    for(int i = 0; i < N; i++){
        dp[i + 1] = D[i] - i * A + ( B * i * (i + 1)) / 2 + deq.get(i);
        deq.add( - (i + 1) * B , dp[i + 1] + (i + 1) * A + ( B * (i + 1) * i) / 2);
    }

    /*output*/
    INT res = INF;
    for(int i = 0; i <= N; i++)
        res = min(res,dp[i] - A * (N -i) + B * (N - i) * (N - i + 1) / 2);
    cout << res << endl;
    return 0;
}