#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==x);
    os << y;
    return os;
}
istream& operator>>(istream &is,INT& x){
    LL y;
    is >> y;
    x = y;
    return is;
}

const INT INF = 1e24;
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*/
    vector<INT> dp(N+1,INF);
    dp[0] = W;
    for(int i = 0; i < N; i++){
        for(int j = 0; j <= i; j++){
            dp[i + 1] = min(dp[i + 1],dp[j] + D[i] - A * (i - j) + B * (i - j) * (i - j + 1)  / 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;
}