#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <vector>
using namespace std;


#define MAXN 300000

int main() {
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);

int n, p, a;
    cin>>n;
    int carrello[n];
    for (a=0; a<n;a++){
        cin>>carrello[a];
    }
    int totale;
    sort(carrello, carrello + n);
    p=0;
    while (p<n) {
        p++;
        totale=totale+carrello[p];
        p++;
        totale=totale+carrello[p];
        p++;
    }
    cout<<totale;
    return 0;
}