#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;

#define MOD 1000000007
#define REP(i, N) for (int i = 0; i < N; ++i)
#define REP1(i, N) for (int i = 1; i <= N; ++i)
#define RREP(i, N) for (int i = N - 1; i >= 0; --i)
#define ALL(a) a.begin(), a.end()

int dp[1010][2];

int main() {
  int n;
  cin >> n;
  int v[n];
  REP(i, n) cin >> v[i];
  REP(i, n) {
    dp[i + 1][0] = max(dp[i][0], dp[i][1]);
    dp[i + 1][1] = dp[i][0] + v[i];
  }
  cout << max(dp[n][0], dp[n][1]) << endl;
  return 0;
}