#include <cstdio>
#include <cstring>
#define MAXN 100000
int v[MAXN + 4];
int d[MAXN + 4];

inline int max2(int a, int b){
  return a > b ? a : b;
}

inline int solve(int n, int st, int dr){
  int i;
  memset(d, 0, sizeof d);
  for(i = st + 1; i <= dr; i++){
    d[i] = d[i - 1];
    if(i - st >= 3)
      if(d[i] < v[i] + v[i - 1])
        d[i] = v[i] + v[i - 1];
    if(d[i] < d[i - 3] + v[i] + v[i - 1])
      d[i] = d[i - 3] + v[i] + v[i - 1];
  }
  return d[dr];
}

int main(){
  freopen("oo.in", "r", stdin);
  freopen("oo.out", "w", stdout);
  int n, i;
  scanf("%d", &n);
  for(i = 0; i < n; i++){
    scanf("%d", &v[i]);
  }
  for(i = 0; i < 4; i++)
    v[i + n] = v[i];
  printf("%d", max2(max2(max2(solve(n, 0, n - 2), solve(n, 1, n - 1)), solve(n, 2, n)), solve(n, 3, n + 1)));
  return 0;
}