#include <bits/stdc++.h>
using namespace std;
const int Nmax = 100005;
int a[Nmax] , n;
int main()
{
    cin >> n;
    for(int i = 1 ; i <= n ; i++)
        cin >> a[i];
    sort(a + 1 , a + n + 1 , greater < int > ());
    long long mx = 0 , sum = 0;
    for(int i = 1 ; i <= n ; i++)
    {
        sum += a[i];
        if(i % 2 == 0)
            mx = max(mx , sum);
    }
    cout << mx << "\n";
    return 0;
}