#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>

using namespace std;


int main() {

	int n =0;
	cin>>n;

	int nums[n] ;

	int tmp=0;
	for(int i=0; i<n;i++){
		cin>>tmp;
		nums[i] =tmp;
	}

	long long all_pattern = pow(2,n);
	bool judge =false;
	int ans=-1;
	for(int i=0; i<all_pattern; i++){
		tmp =0;
		judge =false;
		for(int k=0; k<n; k++){
		/*	cout<<"i:"<<i<<endl;*/
			if((i>>k)%2 ==1){
				if(judge){
					break;
				}
				judge = true;
				tmp += nums[k];
			}else {
				judge =false;
			}
		}
		/*cout<<"tmp:"<<tmp<<endl;*/
		ans = max(ans,tmp);
	}
	cout<<ans<<endl;

	return 0;
}