#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> V(N);
  for (int i = 0; i < N; i++){
    cin >> V[i];
  }
  vector<int> dp0(N + 1, 0);
  vector<int> dp1(N + 1, 0);
  for (int i = 0; i < N; i++){
    dp0[i + 1] = max(dp0[i], dp1[i]);
    dp1[i + 1] = dp0[i] + V[i];
  }
  cout << max(dp0[N], dp1[N]) << endl;
}