原题链接：
https://www.acwing.com/problem/content/106/

 #include<bits/stdc++.h>
using namespace std;
int a[100005];

int main()
{
    int n;
    long long sum;
    while( cin >> n )
    {
        sum=0;
        for( int i=0;i<n;i++ )
            scanf("%d",&a[i]);
        sort(a,a+n);
        for( int i=0;i<n/2;i++ )
        {
            sum+=a[n-i-1]-a[i];
        }
        cout << sum <<endl;
    }
}