#include <cstdio>
#include <algorithm>

using namespace std;

int v[100100];
int x[100100];


int main()
 {
  freopen("oo.in","r",stdin);
  freopen("oo.out","w",stdout);

  int n,i,max, sol = 0, fs = 1, poz = 0;
  #define dim 10000
  char buf[dim];
  fread(buf,1,dim,stdin);
  #define cit(x)                         \
  {                                      \
   x = 0;                                \
   while(buf[poz] < '0')                 \
    {                                    \
     ++poz;                              \
     if(poz == dim)                      \
       fread(buf,1,dim,stdin), poz = 0;  \
    }                                    \
   while(buf[poz] >= '0')                \
    {                                    \
     x = x*10 + buf[poz] - '0';          \
     if(++poz == dim)                    \
      fread(buf,1,dim,stdin), poz = 0;   \
    }                                    \
  }

  cit(n)

  for(i=1;i<=n;++i)
   cit(v[i])

  #define calc1                    \
  max = 0;                         \
  x[fs] = 0;                       \
  x[fs+1] = v[fs+1] + v[fs];       \
  for(i=fs+2;i<n;++i)              \
   {                               \
    x[i] = max + v[i-1] + v[i];    \
    if(x[i-2] > max)               \
     max = x[i-2];                 \
   }                               \
                                   \
  if(max < x[n-1])                 \
    max = x[n-1];                  \
                                   \
  if(sol < max)                    \
   sol = max
   
  #define calc2   v[--fs] = v[n]; --n; calc1;  ++fs;  ++n
  #define calc3   reverse(v+1,v+n); calc1; calc2

  calc1;calc2;calc3;

  printf("%d\n", sol);

  return 0;
 }