#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <limits>
#include <queue>
#include <iomanip>
#include <set>
//#include <bits/stdc++.h>
template<typename T> bool chmax(T &a,T b){if(a<b){a=b;return true;}return false;}
template<typename T> bool chmin(T &a,T b){if(a>b){a=b;return true;}return false;}
using namespace std;
#define ALL(X) X.begin(),X.end()
using ll = long long int;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vvll> vvvll;
const int MOD=1000000007;
//const int MOD=998244353;
const int INTMAX=2147483647;
const ll LLMAX=9223372036854775807;


int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    ll N;
    cin>>N;
    vll L(2*N);
    for(ll i=0;i<2*N;i++)cin>>L[i];
    sort(ALL(L));
    ll ans=0;
    for(ll i=0;i<2*N;i++){
        ans+=L[i];
        i++;
    }
    cout<<ans<<endl;
    
    return 0;
}

#include<stdio.h>
#include<algorithm>
#define reg register
#define ri reg int
#define rep(i, x, y) for(ri i = x; i <= y; ++i)
#define nrep(i, x, y) for(ri i = x; i >= y; --i)
#define DEBUG 1
#define ll long long
#define max(i, j) (i) > (j) ? (i) : (j)
#define min(i, j) (i) < (j) ? (i) : (j)
struct IO {
	#define MAXSIZE (1 << 20)
	#define isdigit(x) (x >= '0' && x <= '9')
	char buf[MAXSIZE], *p1, *p2;
	char pbuf[MAXSIZE], *pp;
	#if DEBUG
	#else
		IO() : p1(buf), p2(buf), pp(pbuf) {}
		~IO() {
			fwrite(pbuf, 1, pp - pbuf, stdout);
		}
	#endif
	inline char gc() {
		#if DEBUG
    		return getchar();
		#endif
    	if(p1 == p2)
			p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin);
    	return p1 == p2 ? ' ' : *p1++;
	}
	inline bool blank(char ch) {
    	return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
	}
	template <class T>
	inline void read(T &x) {
    	register double tmp = 1;
    	register bool sign = 0;
    	x = 0;
    	register char ch = gc();
    	for(; !isdigit(ch); ch = gc())
    		if(ch == '-') sign = 1;
    	for(; isdigit(ch); ch = gc())
			x = x * 10 + (ch - '0');
    	if(ch == '.')
			for(ch = gc(); isdigit(ch); ch = gc())
        		tmp /= 10.0, x += tmp * (ch - '0');
    	if(sign) x = -x;
	}
	inline void read(char *s) {
		register char ch = gc();
		for(; blank(ch); ch = gc());
		for(; !blank(ch); ch = gc())
			*s++ = ch;
    	*s = 0;
	}
	inline void read(char &c) {
    	for(c = gc(); blank(c); c = gc());
	}
	inline void push(const char &c) {
		#if DEBUG
    		putchar(c);
		#else
    		if(pp - pbuf == MAXSIZE) {
				fwrite(pbuf, 1, MAXSIZE, stdout);
				pp = pbuf;
			}
    		*pp++ = c;
		#endif
	}
	template <class T>
	inline void write(T x) {
    	if(x < 0) {
			x = -x;
			push('-');
		}
    	static T sta[35];
    	T top = 0;
    	do{
			sta[top++] = x % 10;
			x /= 10;
    	}while(x);
    	while(top)
			push(sta[--top] + '0');
	}
	template <class T>
	inline void write(T x, char lastChar) {
    	write(x);
		push(lastChar);
	}
} io;
int a[110], n, ans;
int main() {
	io.read(n);
	rep(i, 1, n * 2) io.read(a[i]);
	std::sort(a + 1, a + 2 * n + 1);
	rep(i, 1, n) ans += a[2 * i - 1];
	io.write(ans);
}