#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const ll N = 2e5 + 2;
ll used[N] = {0};
multiset < ll > S;
void remove_max() {
auto R = S.end();
R --;
S.erase(R);
return ;
}
ll find_max() {
auto R = S.end();
R --;
used[*R] = 1;
return (*R);
}
void remove_min() {
auto R = S.begin();
S.erase(R);
return ;
}
ll find_min() {
auto R = S.begin();
used[*R] = 1;
return (*R);
}
int main() {
ll n, m, r, x,s, y, i, j,ind, t, sum;
cin >> n;
ll a[n+ 2];
sum =0;
for (i = 1; i <= n; i ++) {
cin >> a[i];
sum += a[i];
}
sort ( a + 1, a +n + 1);
for (i = n - 2; i >= 1; i-= 3) sum -= a[i];
cout << sum << endl;
}
