#include <bits/stdc++.h>
using namespace std;
const int dy[] = {-1, 0, 1, 0}, dx[] = {0, 1, 0, -1};
const double EPS = 1e-8;
const double PI = acos(-1.0);
int popcount(int n) { return __builtin_popcount(n); }
int popcount(long long n) { return __builtin_popcountll(n); }
template <class T>
int SIZE(T a) {
  return a.size();
}
template <class T>
string IntToString(T num) {
  string res;
  stringstream ss;
  ss << num;
  return ss.str();
}
template <class T>
T StringToInt(string str) {
  T res = 0;
  for (int i = 0; i < SIZE(str); i++) res = (res * 10 + str[i] - '0');
  return res;
}
template <class T>
T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <class T>
void PrintSeq(T &a, int sz) {
  for (int i = 0; i < sz; i++) {
    cout << a[i];
    if (sz == i + 1)
      cout << endl;
    else
      cout << ' ';
  }
}
bool EQ(double a, double b) { return abs(a - b) < EPS; }
void fastStream() {
  cin.tie(0);
  std::ios_base::sync_with_stdio(0);
}
vector<string> split(string str, char del) {
  vector<string> res;
  for (int i = 0, s = 0; i < SIZE(str); i++) {
    if (str[i] == del) {
      if (i - s != 0) res.push_back(str.substr(s, i - s));
      s = i + 1;
    } else if (i == SIZE(str) - 1) {
      res.push_back(str.substr(s));
    }
  }
  return res;
}
int N;
long long as[100001];
long long leftDP[2][100001];
long long rightDP[2][100001];
long long goLeft(int pari, int pos) {
  if (leftDP[pari][pos] >= 0) return leftDP[pari][pos];
  long long res = 0;
  if (pos == 0) {
  } else {
    if (pari == 0) {
      res = max(res,
                goLeft(pari, pos - 1) + as[pos - 1] - (as[pos - 1] % 2 == 0));
      if (as[pos - 1] != 1)
        res = max(res, goLeft(pari ^ 1, pos - 1) + as[pos - 1] -
                           (as[pos - 1] % 2 == 1));
    } else {
      if (as[pos - 1] != 1)
        res = max(res,
                  goLeft(pari, pos - 1) + as[pos - 1] - (as[pos - 1] % 2 == 1));
    }
  }
  return leftDP[pari][pos] = res;
}
long long goRight(int pari, int pos) {
  if (rightDP[pari][pos] >= 0) return rightDP[pari][pos];
  long long res = 0;
  if (pos == N - 1) {
  } else {
    if (pari == 0) {
      res = max(res, goRight(pari, pos + 1) + as[pos] - (as[pos] % 2 == 0));
      if (as[pos] != 1)
        res =
            max(res, goRight(pari ^ 1, pos + 1) + as[pos] - (as[pos] % 2 == 1));
    } else {
      if (as[pos] != 1)
        res = max(res, goRight(pari, pos + 1) + as[pos] - (as[pos] % 2));
    }
  }
  return rightDP[pari][pos] = res;
}
int main() {
  memset(leftDP, -1, sizeof(leftDP));
  memset(rightDP, -1, sizeof(rightDP));
  cin >> N;
  for (int i = 0; i < N - 1; i++) cin >> as[i];
  long long res = 0;
  for (int i = 0; i < N; i++) {
    res = max(res, goLeft(1, i) + goRight(1, i));
    res = max(res, goLeft(1, i) + goRight(0, i));
    res = max(res, goLeft(0, i) + goRight(1, i));
  }
  cout << res << endl;
  return 0;
}
