#include<bits/stdc++.h>
using namespace std;

int n;
int data[1111];
int memo[1111][2];

int solve(int p, bool flg){

  if(p == n) return 0;
  if(memo[p][flg]) return memo[p][flg];
  
  int ret = 0;
  if(!flg)
    ret += max(solve(p+1, true)+data[p], solve(p+1, false));

  else
    ret += solve(p+1, false);

  return memo[p][flg] = ret;
}

int main(){

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

  cout << solve(0, false) << endl;

}