#include<iostream>
#include<cstdio>
#define ll long long
using namespace std;
const int N=1000005;
const ll INF=1e17; 
int n;
ll mn1,mn2,mx;
ll calc(ll a,ll b,ll c)
{
    return -((b*b)/(4*a))+c;
}
int main()
{
    freopen("Unnamed_Problem.in","r",stdin);
    freopen("Unnamed_Problem.out","w",stdout);
    scanf("%d",&n);
    ll k;
    mx=-INF;
    mn1=mn2=INF;
    for(int i=1;i<=n;++i)
    {
        scanf("%lld",&k),mx=max(mx,k);
        if(k<=mn1) mn2=mn1,mn1=k;
        else if(k<mn2) mn2=k;
    }
    ll ans=min(calc(mn1,mx,mn2),calc(mn2,mx,mn1));
    printf("%lld\n",ans);
    return 0;
}