#include <bits/stdc++.h>
using namespace std;

long long brojevi[100005],n,zbir;

int main(){

freopen("pairs.in","r",stdin);
freopen("pairs.out","w",stdout);
  scanf("%lld",&n);
    for(int i=1;i<=n*2;i++)
      {
       scanf("%lld",&brojevi[i]);
      }

sort(brojevi,brojevi+n*2+1);
 for(int i=1;i<=2*n-1;i+=2)
    {
     zbir=zbir+brojevi[i+1]-brojevi[i];
    }


    printf("%lld",zbir);





  return 0;
}