/* -*- coding: utf-8 -*-
 *
 * 45.cc: No.45 回転寿司 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 1000;

/* typedef */

/* global variables */

int vs[MAX_N], dp[MAX_N + 1][2];

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;

  for (int i = 0; i < n; i++) cin >> vs[i];

  for (int i = 0; i < n; i++) {
    dp[i + 1][0] = max(dp[i][0], dp[i][1]);
    dp[i + 1][1] = dp[i][0] + vs[i];
  }

  printf("%d\n", max(dp[n][0], dp[n][1]));
  return 0;
}