#include<iostream>
#include<cstdio>
#define ll long long
#define ld long double
#define MN 1000000
using namespace std;
inline int read()
{int x = 0 , f = 1; char ch = getchar();while(ch < '0' || ch > '9'){ if(ch == '-') f = -1;  ch = getchar();}while(ch >= '0' && ch <= '9'){x = x * 10 + ch - '0';ch = getchar();}return x * f;
}ll f[MN+5],s[MN+5],a,b,c;
int top=0,tail=0,q[MN+5];
int n;ll calc(ll x){return a*x*x+b*x+c;}ld solve(int x,int y)
{return (ld)(f[x]-f[y])/(s[x]-s[y])+(ld)a*(s[x]+s[y])-(ld)b;
}void ins(int x)
{while(top>tail&&solve(x,q[top])>solve(q[top],q[top-1])) top--;q[++top]=x;
}int get(ll x)
{while(top>tail&&solve(q[tail+1],q[tail])>x) tail++;return q[tail];
}int main()
{n=read();a=read();b=read();c=read();for(int i=1;i<=n;i++) s[i]=s[i-1]+read();for(int i=1;i<=n;i++){int from=get(1LL*2*a*s[i]);f[i]=f[from]+calc(s[i]-s[from]);ins(i);}cout<<f[n]; return 0;
}

#include<iostream>
#include<cstdio>
#define MN 100000
using namespace std;
inline int read()
{int x = 0 , f = 1; char ch = getchar();while(ch < '0' || ch > '9'){ if(ch == '-') f = -1;  ch = getchar();}while(ch >= '0' && ch <= '9'){x = x * 10 + ch - '0';ch = getchar();}return x * f;
}struct edge{int to,next,w;}e[MN*2+5];
int head[MN+5],cnt=0,n;
int f[MN+5],w1[MN+5],f1[MN+5],mx[MN+5],mx2[MN+5],ans=0,K,from; void solve(int x,int fa)
{int from1=0,from2=0;mx[x]=mx2[x]=f[x]=0;for(int i=head[x];i;i=e[i].next)if(e[i].to!=fa){solve(e[i].to,x);if(f[e[i].to]+e[i].w>mx[x]) mx2[x]=mx[x],mx[x]=f[e[i].to]+e[i].w,from2=from1,from1=e[i].to;else if(f[e[i].to]+e[i].w>mx2[x]) mx2[x]=f[e[i].to]+e[i].w,from2=e[i].to;}if(mx[x]+mx2[x]>ans) ans=mx[x]+mx2[x],from=x;f[x]=mx[x];mx[x]=from1;mx2[x]=from2;
}void relabel(int x)
{for(int i=head[x];i;i=e[i].next)if(e[i].to==mx[x])e[i].w=-1,relabel(e[i].to);
}void ins(int f,int t)
{e[++cnt]=(edge){t,head[f],1};head[f]=cnt;e[++cnt]=(edge){f,head[t],1};head[t]=cnt;
}int main()
{n=read();K=read();for(int i=1;i<n;i++) ins(read(),read());solve(1,0);if(K==1)return 0*printf("%d",2*n-1-ans);n=n*2-ans;ans=0;for(int i=head[from];i;i=e[i].next)if(e[i].to==mx[from]||e[i].to==mx2[from])e[i].w=-1,relabel(e[i].to);solve(1,0);printf("%d\n",n-ans);return 0;
}

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#define MN 1500
#define ll long long
using namespace std;
inline int read()
{int x = 0 , f = 1; char ch = getchar();while(ch < '0' || ch > '9'){ if(ch == '-') f = -1;  ch = getchar();}while(ch >= '0' && ch <= '9'){x = x * 10 + ch - '0';ch = getchar();}return x * f;
}struct P
{double x,y,alpha;void getAlpha(double xx,double yy){alpha=atan2(x-xx,y-yy);}friend double cross(P a,P b){return a.x*b.y-a.y*b.x;}bool operator == (P b){return x==b.x&&y==b.y;}bool operator < (const P &b) const {return alpha<b.alpha;}P operator - (P b){return (P){x-b.x,y-b.y};}void print(){cout<<x<<" "<<y<<" "<<alpha<<endl;}
}p[MN+5],pt[MN+5];int n,top;
double ans=0;ll work(P th)
{ll sum=1LL*(n-3)*(n-1)*(n-2)/6;int num=0;top=2;for(int i=1;i<n;i++,--num){while(cross(p[i]-th,p[top]-th) <= 0){top=top%(n-1)+1,num++;if(top==i) break;}sum-=1LL*(num)*(num-1)/2; }return sum;
}int main()
{n=read();if(n==3) return 0*puts("3");for(int i=1;i<=n;i++) pt[i].x=p[i].x=read(),pt[i].y=p[i].y=read();for(int i=1;i<=n;i++){for(int j=1;j<n;j++){if(pt[i]==p[j]) swap(p[j],p[n]);p[j].getAlpha(pt[i].x,pt[i].y);    }sort(p+1,p+n);ans+=work(pt[i]);}double A=1LL*n*(n-1)*(n-2)/6,B=1LL*n*(n-1)*(n-2)*(n-3)/24;printf("%.6lf\n",(ans+2*(B-ans))/A+3);return 0;
}