#pragma region GNUC
//以下を参考にした
//https://yukicoder.me/wiki/auto_vectorization
#ifdef __GNUC__
#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#endif
#pragma endregion

#define _USE_MATH_DEFINES

#pragma region
#include <iostream>
#include <iomanip>
#include <stdio.h>

#include <sstream>
#include <algorithm>
#include <cmath>

#include <string>
#include <cstring>
#include <vector>

#include <queue>
#include <complex>
#include <set>
#include <map>
#include <stack>
#include <list>

#include <fstream>
#include <random>
#pragma endregion //#include
/////////
#define REP(i, x, n) for(int i = x; i < n; ++i)
#define rep(i,n) REP(i,0,n)
/////////
#pragma region
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
#pragma endregion //typedef
/////////
//定数
const int INF = (int)1e9;
const int MOD = (int)1e9+7;
const LL LINF = (LL)1e18;
/////////
using namespace::std;
/////////
#pragma region Math
// 最大公約数
template<class T>
inline T gcd(T a, T b){return b ? gcd(b, a % b) : a;}
//inline T gcd(T a, T b){return b == 0 ? a : gcd(b, a % b);}

// 最小公倍数
template<class T>
inline T lcm(T a, T b){return a / gcd(a, b) * b;}
//inline T lcm(T a, T b){return a * b / gcd(a, b);}
#pragma endregion //math
#pragma region
template<class T>
void UNIQUE(vector<T>& vec){
	sort(vec.begin(),vec.end());
	vec.erase(unique(vec.begin(),vec.end()),vec.end() );
}
#pragma endregion // sort erase unique
////////////////////////////////
struct edge{int to;LL cost;};
edge make_edge(int to,LL cost){
	edge ret = {to,cost};
	return ret;
}
#pragma region //グラフ
void dijkstra(int root,int V,vector<LL>& dist,
	vector< vector<edge> > G	){
	priority_queue<pair<LL,int>,vector<pair<LL,int> >,greater<pair<LL,int> > > que;
	dist.assign(V,LINF);
	dist[root] = 0;
	que.push(pair<LL,int>(0,root));//距離、頂点番号

	while( !que.empty() ){
		pair<LL,int> p = que.top();que.pop();
		int v = p.second;
		if( dist[v] < p.first ) continue;
		for(int i=0;i < (int)G[v].size();++i){
			edge e = G[v][i];
			if( dist[e.to] > dist[v] + e.cost ){
				dist[e.to] = dist[v] + e.cost;
				que.push(pair<LL,int>(dist[e.to],e.to));
			}
		}
	}
}
#pragma endregion //ダイクストラ法:O(|E|log|V|)
#pragma region //グラフ
void warshall_floyd(vector<vector<LL> >& dist,int V,const LL INF=LINF){
	for(int k=0;k<V;++k){
		for(int i=0;i<V;++i){
			if( dist[i][k] >= INF ) continue;
			for(int j=0;j<V;++j){
				if( dist[k][j] >= INF )continue;
				dist[i][j] = min(dist[i][j],dist[i][k]+dist[k][j]);
			}
		}
	}
}
#pragma endregion //ワーシャルフロイド:O(|V|**3)
#pragma region 
//http://sugarknri.hatenablog.com/entry/2016/07/16/165715
//LL inv[1000010];
void makeinv(vector<LL>& inv,const LL P){
	int i;
	inv = vector<LL>(1000010,0);
	inv[1]=1;
	for(i=2;i<=1000000;i++){
		inv[i] = inv[P%i] * (P-P/i)%P;//OVF
	}
}

ULL nCk(ULL N,ULL k){
	static vector<LL> inv;
	if( inv.size() == 0 ){
		makeinv(inv,MOD);
	}
	k = min(k,N-k);
	if( k == 0 ){return 1;}
	if( k == 1 ){return N%MOD;}
	ULL ret = 1;
	for(int i=1;i<=k;++i){
		ret *= ((N+1-i)*inv[i])%MOD;//OVF
		ret %= MOD;
	}
	return ret;
}
#pragma endregion //組み合わせnCk(,10^5)
#pragma region CGL
class Point{
public:
	double x,y;
	Point(double x=0,double y=0):x(x),y(y){}

	Point	operator +	(Point p){return Point(add(x,p.x),add(y,p.y));}
	void	operator +=	(Point p){x=add(x,p.x);y=add(y,p.y);}
	Point	operator -	(Point p){return Point(add(x,-p.x),add(y,-p.y));}
	void	operator -=	(Point p){x=add(x,-p.x);y=add(y,-p.y);}
	Point	operator *	(double a){return Point(x*a,y*a);}
	double	operator *	(Point p){return dot(p);}
	Point	operator /	(double a){return Point(x/a,y/a);}

	double norm(){return sqrt(x*x+y*y);}
	double dot(Point p){return add(x*p.x,y*p.y);}
	double rot(Point p){return add(x*p.y,-y*p.x);}
	double add(double a,double b){
		double EPS = 1e-10;
		if( abs(a+b) < EPS*(abs(a)+abs(b)) ){
			return 0;
		}
		return a+b;
	}
};
istream& operator>>(istream& in,Point& P){
	in >> P.x >> P.y;
	return in;
}

//線分p1-p2上に点qがあるか判定
bool on_seg(Point p1,Point p2,Point q){
	return (p1-q).rot(p2-q) == 0 && (p1-q).dot(p2-q) <= 0;
}
Point intersection(Point p1,Point p2,Point q1,Point q2){
	return p1+(p2-p1)*((q2-q1).rot(q1-p1)/(q2-q1).rot(p2-p1));
}
enum PointPotion{ON_SEGMENT,COUNTER_CLOCKWISE,ONLINE_BACK,CLOCKWISE,ONLINE_FRONT};
PointPotion ccw(Point A,Point B,Point C){
	B -= A;C -=A;
	if( B.rot(C) > 0 ) return COUNTER_CLOCKWISE;
	if( B.rot(C) < 0 ) return CLOCKWISE;
	if( B.dot(C) < 0 ) return ONLINE_BACK;
	if( B.norm() < C.norm() ) return ONLINE_FRONT;
	return ON_SEGMENT;
}
#pragma endregion //class Point
#pragma region
//辞書順で比較
bool cmp_x(const Point& p,const Point& q){
	if( p.x != q.x ) return p.x < q.x;
	return p.y < q.y;
}

//凸包を求める
vector<Point> convex_hull(vector<Point> ps,int n){
	sort(ps.begin(),ps.end(), cmp_x);
	int k = 0;//凸包の頂点数
	vector<Point> qs(n*2);//構築中の凸包
	//下側の凸包の作成
	for(int i=0;i<n;++i){
		while(k>1 && (qs[k-1]-qs[k-2]).rot(ps[i]-qs[k-1]) <=0){
			k--;
		}
		qs[k++] = ps[i];
	}
	//上側凸包の作成
	for(int i=n-2,t=k;i>=0;i--){
		while(k>t && (qs[k-1]-qs[k-2]).rot(ps[i]-qs[k-1]) <=0){
			k--;
		}
		qs[k++] = ps[i];
	}
	qs.resize(k-1);
	return qs;
}
#pragma endregion //凸包
#pragma region 
template<class T,class U>
istream& operator>>(istream& in,pair<T,U> P){
	in >> P.first >> P.second;
	return in;
}
#pragma endregion //cin pair<T,U>
#pragma region 
#pragma endregion //
const double PI = acos(-1.0);
const double EPS = 1e-9;

void solve(){
	int N;
	cin >> N;
	vector<int> L(2*N);
	for(int i=0;i<2*N;++i){
		cin >> L[i];
	}
	sort(L.begin(), L.end());
	int ans = 0;
	for(int i=0;i<N;++i){
		ans += L[i*2];
	}
	cout << ans << endl;
}

#pragma region main
signed main(void){
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	std::cout << std::fixed;//小数を10進数表示
	cout << setprecision(16);//小数点以下の桁数を指定
	
	solve();
}
#pragma endregion //main()

Measured memory_bytes: 256