#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=2e9+1;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}

template<typename T,typename Compare=less<T>>
vector<pair<int,T>> monotone_minima(int H,int W,const function<T(int,int)> &f,const Compare &comp=Compare()){
    vector<pair<int,T>> dp(H);
    function<void(int,int,int,int)> dfs=[&](int top,int bottom,int left,int right){//閉区間で実装
        if(top>bottom)return;
        int line=(top+bottom)/2;
        T val=f(line,left);
        int idx=left;
        for(int i=left;i<=right;i++){
            T nowval=f(line,i);
            if(comp(nowval,val)){
                val=nowval;
                idx=i;
            }
        }
        dp[line]=make_pair(idx,val);
        dfs(top,line-1,left,idx);
        dfs(line+1,bottom,idx,right);
    };
    dfs(0,H-1,0,W-1);
    return dp;
}

ll n,a,b,w;
vl dp,d,fin;
ll basej,basei;
auto fx=[](ll i,ll j){
  ll len=(basei+i)-(basej+j)-1;
  return dp[basej+j]-a*len+len*(len+1)/2*b;
};
void induce(ll l,ll m,ll r){
  basei=m;basej=l;
  for(int i=l;i<m;i++){
    if(!fin[i]){
      dp[i]+=d[i];
      fin[i]=1;
    }
  }
  auto ans=monotone_minima<ll>(r-m,m-l,fx);
  for(int i=m;i<r;i++){
    chmin(dp[i],ans[i-m].second);
  }
}
void solve(ll l,ll r){
  if(l+1==r)return;
  ll m=(l+r)/2;
  solve(l,m);
  induce(l,m,r);
  solve(m,r);
}
int main(){
  cin >> n >> a >> b >> w;
  d.resize(n+2);dp.resize(n+2,INF);fin.resize(n+2); 
  dp[0]=w;
  rep(i,n)cin >> d[i+1];
  solve(0,n+2);
  cout << dp.back() << endl;
}