#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,m[1000001],ans;
int main()
{
	freopen("Unnamed_Problem.in","r",stdin);
	freopen("Unnamed_Problem.out","w",stdout);
	memset(m,0,sizeof(m));
	cin>>n;
    for(int i=1;i<=n;i++)cin>>m[i];
    sort(m+1,m+n+1);
    /*
    for(int i=1;i<=n;i++)
    	for(int j=1;j<=n;j++)
        	for(int k=1;k<=n;k++)
        	{
        	    if(i!=j && j!=k && i!=k)
        	    {
        	        double a=m[i],b=m[j],c=m[k];
            	    double x=-b/2*a;//对称轴横坐标 
            	    double y=a*x*x+b*x+c;//最低点纵坐标 
            	    if(y<ans)ans=y;
                }
            }
    */
	double a,b,c,y1,y2;
	c=m[1]; b=m[n]; a=m[2];
	y1 = c - b*b/4/a;
	c=m[2]; b=m[n]; a=m[1];
	y2 = c - b*b/4/a;
	ans=min((ll)y1,(ll)y2);//最小值位置(-b/2a,c-b*b/4a) 
	cout<<ans<<endl;
	return 0;
}