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https://codeforces.com/contest/1092/problem/B

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=10000;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int a[N];
int main()
{
#ifdef DEBUG
	freopen(\"input.in\", \"r\", stdin);
	//freopen(\"output.out\", \"w\", stdout);
#endif
    scanf(\"%d\",&n);
    for(int i=1;i<=n;i++)
        scanf(\"%d\",&a[i]);
    sort(a+1,a+n+1);
    int ans=0;
    for(int i=1;i<=n/2;i++){
        ans+=abs(a[2*i-1]-a[2*i]);
    }
    cout << ans << endl;
    //cout << \"Hello world!\" << endl;
    return 0;
}