#include <iostream>
using namespace std;

int main(){
   int ans = 0,n;
   cin >> n;
   int v[n],dp[n];
   for(int i = 0;i < n;i++) cin >> v[i];
   for(int i = 0;i < n;i++){
      dp[i] = v[i];
      if(i > 0) dp[i] = max(dp[i],dp[i - 1]);
      if(i > 1) dp[i] = max(dp[i],dp[i - 2] + v[i]);
      ans = max(ans,dp[i]);
   }
   for(int i = 0;i < n - 1;i++){
      dp[i] = v[i + 1];
      if(i > 0) dp[i] = max(dp[i],dp[i - 1]);
      if(i > 1) dp[i] = max(dp[i],dp[i - 2] + v[i + 1]);
      ans = max(ans,dp[i]);
   }
   cout << ans << endl;
}