#include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>

#define INF (2 << 28)
#define fr first
#define sc second
using namespace std;

typedef long long ll;
typedef pair<int, int> iP;

int n, v[1111];
int dp[1111][2];

int rec(int idx, int prev){
  
  if(idx == n) return 0;
  if(dp[idx][prev]) return dp[idx][prev];
  
  int ret = rec(idx + 1, 0);
  if(!prev) ret = max(ret, rec(idx + 1, 1) + v[idx]);

  return dp[idx][prev] = ret;
}
  
int main(){
  
  cin >> n;
  for(int i = 0; i < n; i++) cin >> v[i];
  
  cout << rec(0, 0) << endl;
}