#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define REP(i,n) FOR(i,0,n)
#define pb push_back
#define en "\n"
#define ITER(i,a) for( typeof(a.begin()) i=a.begin();i!=a.end();i++)
#define mod 1000000007
#define mpp make_pair
#define mes(a,b) memset((a),(b),sizeof((a))
typedef map<int,int> MI;
typedef pair<int,int>   PI;
typedef vector<int> VI;
typedef long long int LL;

int main() {
	// your code goes here
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n;
    cin>>n;
    n=(2*n);
    int a[n];
    for(int i=0;i<n;i++)
    cin>>a[i];
    sort(a,a+n);
    int ans=0;
    for(int i=0;i<n;i+=2)
    {
        ans=ans+a[i];
    }
    cout<<ans;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;

typedef int64_t Int;
#define all(x) (x).begin(), (x).end()
 
const double EPS = 1e-10;
const Int INF = 1e18;
const int inf = 1e9;
const Int mod = 1e9+7;

bool print_space_enable = false;
void print() { 
    cout << '\n'; 
    print_space_enable = false;
}

template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
    if (print_space_enable) std::cout << " ";
    cout << fixed << setprecision(15) << head;
    print_space_enable = true;
    print(std::forward<Tail>(tail)...);
}

template<typename T>
void print(vector<T> v) {
    for (size_t i = 0; i < v.size(); i++) {
        if (i > 0) std::cout << " ";
        std::cout << v[i];
    }
    std::cout << '\n';
}

void solve() {
    Int n;
    cin >> n;
    vector<Int> a(2 * n);
    for (Int i = 0; i < 2 * n; i++) {
        cin >> a[i];
    }
    sort(all(a));
    Int res = 0;
    for (Int i = 0; i < 2 * n; i += 2) {
        res += a[i];
    }
    print(res);
}

int main() {
    solve();
    return 0;
}
