#include<bits/stdc++.h>
using namespace std;
int n,a[55],dp[55],s;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
	{
        cin>>a[i];
        dp[i]=a[i];
        for(int j=1;j<=i-2;j++)
		{
            dp[i]=max(dp[i],dp[j]+a[i]);
        }
        s=max(s,dp[i]);
    }
    cout<<s;
}
/**************************************************************
	Problem: 1653
	User: hongyipin
	Language: C++
	Result: Accepted
	Time:26 ms
	Memory:2072 kb
****************************************************************/