#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	int a[205],n;
	cin>>n;
	for(int i=0;i<2*n;i++)
		cin>>a[i]; 
	sort(a,a+2*n);
	int count=0;
	for(int i=0;i<2*n;i+=2)
		count+=a[i];
	cout<<count;
	return 0;
} 
