var f:array[1..20010] of longint;

i,j,k,n,m,ans:longint;

begin

readln(n);

for i:=1 to n do read(f[i]);

for i:=0 to n do

if f[i]+f[i+1]>ans then ans:=f[i]+f[i+1];

if f[1]+f[n]>ans then ans:=f[1]+f[n];

for i:=1 to n do m:=m+f[i];

k:=trunc(m div (n div 2))+1;

if k>ans then ans:=k;

writeln(ans);

end.