#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <sstream>
#include <vector>
#include <map>
#include <set>
#include <deque>
#include <list>
#include <stack>
#include <queue>
#include <complex>
#include <ctime>
#include<cstdlib>
#define _USE_MATH_DEFINES
#include <math.h>
#include<cmath>
#include <cstdarg> 
#include <iomanip>

#include<unordered_map>
#include<unordered_set>
//#include <arra.y>

//#define  NDEBUG
#include <assert.h>

using namespace std;

#define dprint(Exp,...) if(Exp){fprintf(stderr, __VA_ARGS__);}
#define printe(...) fprintf(stderr, __VA_ARGS__);
#define PrtExp(_Exp)  cerr<< #_Exp <<" = "<< (_Exp)
#define PrtExpN(_Exp)  cerr<< #_Exp <<" = "<< (_Exp) <<"\n"

#define SINT(n) scanf("%d",&n);
#define SINT2(n,m) scanf("%d %d",&n,&m);
#define SINT3(n,m,o) scanf("%d %d %d",&n,&m,&o);
#define SINT4(n,m,o,p) scanf("%d %d %d %d",&n,&m,&o,&p);
#define SINT5(n,m,o,p,q) scanf("%d %d %d %d %d",&n,&m,&o,&p,&q);
//#define SLL(n) scanf("%I64d",&n);
#define SLL(n) scanf("%lld",&n);
#define SLL2(n,m) scanf("%lld %lld",&n,&m);
#define SLL3(n,m,o) scanf("%lld %lld %lld",&n,&m,&o);
#define SST(s) scanf("%s",s);
#define SCH(c) scanf("%c",&c);

#define GC() getchar();

#define PINT(n) printf("%d",(int)(n));
#define PINT2(n,m) printf("%d %d",(int)(n),(int)(m));
#define PINT3(n,m,l) printf("%d %d %d",(int)(n),(int)(m),(int)(l));
//#define PLL(n) printf("%I64d",(long long)(n));
#define PLL(n) printf("%lld",(long long)(n));
#define PST(s) printf("%s",(s));
#define PCH(s) printf("%c",(s));

#define PINTN(n) printf("%d\n",(int)(n));
#define PINT2N(n,m) printf("%d %d\n",(int)(n),(int)(m));
#define PINT3N(n,m,l) printf("%d %d %d\n",(int)(n),(int)(m),(int)(l));
//#define PLLN(n) printf("%I64d\n",(long long)(n));
#define PLLN(n) printf("%lld\n",(long long)(n));
#define PSTN(s) printf("%s\n",(s));
#define PCHN(s) printf("%c\n",(s));

#define PSP() printf(" ");
#define PN() printf("\n");

#define PC(c) putchar(c);
#define CSP (' ')
#define SN ("\n")

#define rep(i,a) for(i=0;i<a;i++)
#define reP(i,a) for(i=0;i<=a;i++)
#define Rep(i,a) for(i=a-1;i>=0;i--)
#define ReP(i,a) for(i=a;i>=0;i--)

#define rEp(i,a) for(int i=0;i<a;i++)
#define rEP(i,a) for(int i=0;i<=a;i++)
#define REp(i,a) for(int i=a-1;i>=0;i--)
#define REP(i,a) for(int i=a;i>=0;i--)

#define repft(i,a,b) for(i=a;i<b;i++)
#define repfT(i,a,b) for(i=a;i<=b;i++)
#define Repft(i,a,b) for(i=a-1;i>=b;i--)
#define RepfT(i,a,b) for(i=a;i>=b;i--)

#define foreach(a,it) for(auto it = a.begin(); it != a.end(); ++it)

#define FILL(a,v) fill(begin(a),end(a), v)
#define FILL0(a) memset(a,0,sizeof(a))
#define FILL1(a) memset(a,-1,sizeof(a))

typedef long long ll;
typedef unsigned long ul;
typedef pair<int, int> Pi;
typedef pair<ll, ll>   Pl;


const int INF = 0x1f1f1f1f;//522,133,279
const ll INFLL = 0x1f1f1f1f1f1f1f1fLL;//2,242,545,357,980,376,863

template <class A, class B> inline ostream& operator<<(ostream& st, const pair<A, B>& P){ return st<<"("<<P.first<<","<<P.second<<")"; };
template <class A, class B> inline pair<A, B> operator+(const pair<A, B>& P, const pair<A, B>& Q){ return pair<A, B>(P.first+Q.first, P.second+Q.second); };
template <class A, class B> inline pair<A, B> operator-(const pair<A, B>& P, const pair<A, B>& Q){ return pair<A, B>(P.first-Q.first, P.second-Q.second); };

ll bitcount(ll bits){
	bits = (bits&0x5555555555555555)+(bits>>1&0x5555555555555555);
	bits = (bits&0x3333333333333333)+(bits>>2&0x3333333333333333);
	bits = (bits&0x0f0f0f0f0f0f0f0f)+(bits>>4&0x0f0f0f0f0f0f0f0f);
	bits = (bits&0x00ff00ff00ff00ff)+(bits>>8&0x00ff00ff00ff00ff);
	bits = (bits&0x0000ffff0000ffff)+(bits>>16&0x0000ffff0000ffff);
	return (bits&0x00000000ffffffff)+(bits>>32&0x00000000ffffffff);
}





int L[300];

int main(){
	int n;

	int i;
	int r = 0;

	SINT(n);
	rep(i, n*2)SINT(L[i]);
	sort(L, L+n*2);
	for(int i = 0; i<n*2; i += 2){
		r += L[i];
	}
	PINTN(r);

}

Measured memory_bytes: 256