#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int n;
	cin>>n;
	
	vector<long long> a(2*n);
	rep(i,n*2)cin>>a[i];
	
	sort(a.begin(),a.end());
	
	long long ans = 0LL;
	
	rep(i,n){
		ans += a[i*2] * a[i*2+1];
	}
	
	cout<<ans<<endl;
	
    return 0;
}