#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int dp[1005][2];

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