#include <cstdio>

template <typename T> T read();
template <typename T> void write(T, char);
template <typename T> T min(T, T);
template <typename T> T max(T, T);

const int MAXN = 1e6 + 10;

int n;
int a[MAXN];
int maxx = -1;

inline int dis(int i, int j) {
  return min(j - i, n - (j - i));
}

int main() {
  freopen("strategic.in", "r", stdin);
  freopen("strategic.out", "w", stdout);
  n = read<int>();
  for (int i = 1; i <= n; ++i) {
    a[i] = read<int>();
  }

  for (int i = 1; i <= n; ++i) {
    for (int j = i + 1; j <= n; ++j) {
      maxx = max(maxx, dis(i, j) + a[i] + a[j]);
    }
  }

  write(maxx, '\n');
  return 0;
}

template <typename T> T min(T x, T y) {
  return x < y ? x : y;
}

template <typename T> T max(T x, T y) {
  return x > y ? x : y;
}

#define isdigit(ch) (ch >= '0' && ch <= '9')
template <typename T> T read() {
  T res = 0, f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar())
    if (ch == '-') f = -1;
  for (; isdigit(ch); ch = getchar()) res = (res << 3) + (res << 1) + (ch ^ 48);
  return res * f;
}

template <typename T> void write(T x, char ed) {
  if (x < 0) x = -x, putchar('-');
  static int sta[sizeof(T) << 2], top = 0;
  do {
    sta[++top] = x % 10;
    x /= 10;
  } while (x);
  while (top) {
    putchar(sta[top--] ^ 48);
  }
  putchar(ed);
}