#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
/*
*/



int main() {
  int N;
  cin >> N;
  vector<int> V(N);
  rep(i,N){
      cin >> V[i];
  }
  vector<vector<int>> dp(N+10, vector<int>(2));
  dp[0][1] = V[0];
  dp[0][0] = 0;

  for(int i = 0;i<N-1;i++){
      dp[i+1][1] = dp[i][0] + V[i+1];
      dp[i+1][0] = max(dp[i][1],dp[i][0]);
  } 
  int ans = max(dp[N-1][1],dp[N-1][0]);
  cout << ans << endl;
  
 }