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

#ifdef SG
        #include <debug.h>
#else
        #define show(...)
        #define debug(...)
        #define deepen(...)
        #define timer(...)
#endif                                                                                                                                                                                               
                                                                                                                                                                                                     
#define ARG4(_1,_2,_3,_4,...) _4                                                                                                                                                                     
                                                                                                                                                                                                     
#define forn3(i,l,r) for (int i = int(l); i < int(r); ++i)                                                                                                                                           
#define forn2(i,n) forn3 (i, 0, n)                                                                                                                                                                   
#define forn(...) ARG4(__VA_ARGS__, forn3, forn2) (__VA_ARGS__)                                                                                                                                      
                                                                                                                                                                                                     
#define ford3(i,l,r) for (int i = int(r) - 1; i >= int(l); --i)                                                                                                                                      
#define ford2(i,n) ford3 (i, 0, n)                                                                                                                                                                   
#define ford(...) ARG4(__VA_ARGS__, ford3, ford2) (__VA_ARGS__)                                                                                                                                      
                                                                                                                                                                                                     
#define ve vector                                                                                                                                                                                    
#define pa pair                                                                                                                                                                                      
#define tu tuple
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define fs first
#define sc second
#define all(a) (a).begin(), (a).end()
#define sz(a) ((int)(a).size())

typedef long double ld;
typedef int64_t ll;
typedef uint64_t ull;
typedef uint32_t ui;
typedef uint16_t us;
typedef uint8_t uc;
typedef pa<int, int> pii;
typedef pa<int, ll> pil;
typedef pa<ll, int> pli;
typedef pa<ll, ll> pll;
typedef ve<int> vi;

const ld pi = 3.1415926535897932384626433832795l;

template<typename T> inline auto sqr (T x) -> decltype(x * x) {return x * x;}
template<typename T1, typename T2> inline bool umx (T1& a, T2 b) {if (a < b) {a = b; return 1;} return 0;}
template<typename T1, typename T2> inline bool umn (T1& a, T2 b) {if (b < a) {a = b; return 1;} return 0;}

struct Input {

    int n;
    vi l;

        bool read () {
        if (scanf("%d", &n) != 1) return 0;
        l.resize(2 * n);
        forn (i, 2 * n) {
            scanf("%d", &l[i]);
        }
                return 1;
        }

        void init (const Input &input) {
                *this = input;
        }
};

struct Data: Input {

    int ans;

        void write () {
                printf("%d\n", ans);
        }
};

struct Solution: Data {

        void solve () {
            ans = 0;
        sort(all(l));
        forn (i, n) {
            ans += l[2 * i];
        }
        }

        void clear () {
                *this = Solution();
        }
};

Solution sol;

int main () {
        cout.setf(ios::showpoint | ios::fixed);
        cout.precision(20);
#ifdef SG
        while (sol.read()) {
                sol.solve();
                sol.write();
                sol.clear();
        }
#else
        sol.read();
        sol.solve();
        sol.write();
#endif
        return 0;
}

Measured memory_bytes: 256