#include<bits/stdc++.h>
#define endl '\n'
#define ll unsigned long long
using namespace std;
string res="0";
ll a[200002],n,tmp,prenos;
void add(string &res,ll num)
{
    prenos = 0;
    for(int i=res.size()-1;i>=0;i--)
    {
        tmp = prenos+num%10+ (ll)(res[i]-'0');
        res[i] = char(tmp%10 + '0');
        prenos = tmp/10;
        num/=10;
    }
    num+=prenos;
    if(num)
    {
        while(num>0)
        {
            res = char(num%10+'0') + res;
            num/=10;
        }
    }
}
int main()
{
    freopen("pairs.in","r",stdin);
    freopen("pairs.out","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n;
    for(int i=0;i<n*2;i++)
    {
        cin>>a[i];
    }
    sort(a,a+2*n);
    for(int i=0;i<2*n-1;i+=2)
    {
        add(res,a[i+1]-a[i]);
    }
    cout<<res<<endl;
}