/*
* C++11 code template for contests.
* @author: Andrey Kalendarov
* @e-mail: andreykalendarov@gmail.com
*/

/*______ DEFINES _______*/

#define _SCL_SECURE_NO_WARNINGS
#define _CRT_SECURE_NO_WARNINGS
//#define ANDREIKKAA_TOPCODER
//#define ANDREIKKAA_ALLOCATOR
#define ANDREIKKAA_CLASS Solution
#define ANDREIKKAA_METHOD solve
#define ANDREIKKAA_PARAMETERS void
#define ANDREIKKAA_CALL
#define ANDREIKKAA_RETURN_TYPE void
typedef long long ll;
typedef long double ld;
#define x first
#define y second
const int MEMORY_LIMIT_MB = 200;
const int TIME_LIMIT_S = 1;
const char input_filename[] =
#if defined(ANDREIKKAA)
"input.txt"
#else
""
#endif
;
const char output_filename[] =
#if defined(ANDREIKKAA)
""
#else
""
#endif
;

/* ______ INCLUDES ______ */
#include <cassert>
#include <ciso646>
#include <climits>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <array>
#include <bitset>
#include <deque>
#include <forward_list>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <algorithm>
#include <complex>
#include <functional>
#include <initializer_list>
#include <iterator>
#include <limits>
#include <locale>
#include <numeric>
#include <regex>
#include <string>
#include <utility>
#include <fstream>
#include <iostream>
#include <sstream>
#include <iomanip>
using namespace std;

/* _____ ALLOCATION _____ */

#if defined(ANDREIKKAA_ALLOCATOR)
char alloc_memory[MEMORY_LIMIT_MB * 1000 * 1000];
size_t alloc_pointer = 0;
inline void* operator new(size_t x) { alloc_pointer += x; return alloc_memory + alloc_pointer - x; }
inline void operator delete(void*) { }
#endif

/*____ I-O OPERATORS ____*/
template<typename T, typename U> inline ostream &operator<<(ostream &out, const pair<T, U> &p) { out << p.first << ' ' << p.second; return out; }
template<typename T, typename U> inline istream &operator >> (istream &in, pair<T, U> &p) { in >> p.first >> p.second; return in; }
template<typename T> inline ostream &operator<<(ostream &out, const vector<T> &v) { if (v.empty()) return out; out << v.front(); for (auto it = ++v.begin(); it != v.end(); ++it) out << ' ' << *it; return out; }
template<typename T> inline istream &operator >> (istream &in, vector<T> &v) { for (auto &i : v) in >> i; return in; }

/* ________ CODE ________ */

inline ANDREIKKAA_RETURN_TYPE mainFunction(ANDREIKKAA_PARAMETERS)
{
	int n;
	cin >> n;
	vector<int> v(2 * n);
	cin >> v;
	sort(v.begin(), v.end());
	int ans = 0;
	for (int i = 0; i < v.size(); i += 2)
		ans += v[i];
	cout << ans << endl;
}

class ANDREIKKAA_CLASS
{
public:
	ANDREIKKAA_RETURN_TYPE ANDREIKKAA_METHOD(ANDREIKKAA_PARAMETERS)
	{
		if (input_filename[0] != '\0')
			freopen(input_filename, "r", stdin);
		if (output_filename[0] != '\0')
			freopen(output_filename, "w", stdout);
		cin.tie(nullptr);
		ios_base::sync_with_stdio(false);
		//cout << setprecision(20);
		//cout << fixed;
		return mainFunction(ANDREIKKAA_CALL);
	}
#if defined(ANDREIKKAA)
	inline ANDREIKKAA_CLASS() { _start = clock(); }
	inline ~ANDREIKKAA_CLASS() { cerr << "Time: " << (clock() - _start) / (ld)CLOCKS_PER_SEC << endl; }
private:
	time_t _start;
#endif
};

#if defined(ANDREIKKAA) || !defined(ANDREIKKAA_TOPCODER)
int main()
{
	auto _s = new ANDREIKKAA_CLASS; _s->ANDREIKKAA_METHOD(ANDREIKKAA_CALL); delete _s;
#if defined(ANDREIKKAA)
	while (true);
#endif
}
#endif


Measured memory_bytes: 256