#include <bits/stdc++.h> #define int long long using namespace std; int n,a[200005],chose[200005],cnt; double ans; void dfs(int id,double sum,double av,int num,int avid){ if(id==n+1){ ans=max(ans,sum/(double)num-av); return ; } if(num%2==0){ chose[++cnt]=a[id]; dfs(id+1,sum+a[id],(double)chose[avid+1],num+1,avid+1); cnt--; dfs(id+1,sum,av,num,avid); } else{ chose[++cnt]=a[id]; dfs(id+1,sum+a[id],(chose[avid]+chose[avid+1])/2.0,num+1,avid); cnt--; dfs(id+1,sum,av,num,avid); } } signed main(){ scanf("%lld",&n); for(int i=1;i<=n;i++) scanf("%lld",&a[i]); sort(a+1,a+1+n); dfs(1,0,0,0,0); printf("%.4f",ans); return 0; }