#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <set>
#include <map>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

typedef long long ll;

int main() {

  int N; cin >> N;
  int v[N];
  rep(i, N) {
    cin >> v[i];
  }

  ll dp[N+1][2]; rep(i, N+1) rep(j, 2) dp[i][j] = 0;
  dp[0][0] = 1;
  REP(i, 1, N+1) {
    rep(j, i) {
      if(j < i-1) dp[i][0] = max({dp[i][0], dp[j][0] + v[i-1], dp[j][1] + v[i-1]});
      else { dp[i][1] = max(dp[i][1], dp[j][0] + v[i-1]); }
    }
  }
  cout << max(dp[N][0], dp[N][1]) << endl;

  return 0;
}