#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,v;cin>>n;vector A(n+1,vector<int>(2,0));
  for(int i=1;i<=n;i++){
    cin>>v;
    A[i][0]=max(A[i-1][0],A[i-1][1]);
    A[i][1]=A[i-1][0]+v;
  }
  cout<<max(A[n][0],A[n][1]);
}