#include <bits/stdc++.h>
using namespace std;
unsigned long long min(unsigned long long x, unsigned long long y) {
  if (x < y) return x;
  return y;
}
unsigned long long max(unsigned long long x, unsigned long long y) {
  if (x < y) return y;
  return x;
}
long long min(long long x, long long y) {
  if (x < y) return x;
  return y;
}
long long max(long long x, long long y) {
  if (x < y) return y;
  return x;
}
double min(double x, double y) {
  if (x < y) return x;
  return y;
}
double max(double x, double y) {
  if (x < y) return y;
  return x;
}
unsigned long long gcd(unsigned long long x, unsigned long long y) {
  if (!x) return y;
  if (!y) return x;
  if (x > y) swap(x, y);
  return gcd(x, y % x);
}
unsigned long long inv(unsigned long long a, unsigned long long c) {
  if (a == 1) {
    return 1;
  }
  return ((c - (c / a)) * inv(c % a, c)) % c;
}
void printv(vector<int> &a) {
  int n = a.size();
  for (int i = 0; i < n; ++i) {
    cout << a[i] << " ";
  }
  cout << " END\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  long long a[2 * n], x = 0, y = 0, ans = 0;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    a[i + n] = a[i];
    if (i & 1)
      y += a[i];
    else
      x += a[i];
  }
  ans = x;
  for (int i = n; i < 2 * n; ++i) {
    long long temp = x;
    x = y + a[i];
    y = temp - a[i - n];
    ans = max(ans, x);
  }
  cout << ans << "\n";
  return 0;
}
