#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  vector dp(n, vector<int>(2, 0));
  rep(i, n) {
    dp[i][1] = max((i >= 2 ? dp[i - 2][1] : 0), (i >= 1 ? dp[i - 1][0] : 0)) + a[i];
    if (i >= 1) dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
  }
  cout << max(dp[n - 1][0], dp[n - 1][1]) << endl;
  return 0;
}