There are nn students in a university. The number of students is even. The ii-th student has programming skill equal to aiai.

The coach wants to form n2n2 teams. Each team should consist of exactly two students, and each student should belong to exactly one team. Two students can form a team only if their skills are equal (otherwise they cannot understand each other and cannot form a team).

Students can solve problems to increase their skill. One solved problem increases the skill by one.

The coach wants to know the minimum total number of problems students should solve to form exactly n2n2 teams (i.e. each pair of students should form a team). Your task is to find this number.

Input

The first line of the input contains one integer nn (2≤n≤1002≤n≤100) — the number of students. It is guaranteed that nn is even.

The second line of the input contains nn integers a1,a2,…,ana1,a2,…,an (1≤ai≤1001≤ai≤100), where aiai is the skill of the ii-th student.

Output

Print one number — the minimum total number of problems students should solve to form exactly n2n2 teams.

Examples

input

Copy

6
5 10 2 3 14 5

output

Copy

5

input

Copy

2
1 100

output

Copy

99

Note

In the first example the optimal teams will be: (3,4)(3,4), (1,6)(1,6) and (2,5)(2,5), where numbers in brackets are indices of students. Then, to form the first team the third student should solve 11 problem, to form the second team nobody needs to solve problems and to form the third team the second student should solve 44 problems so the answer is 1+4=51+4=5.

In the second example the first student should solve 9999 problems to form a team with the second one.

#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
	int a[1100];
	int n,m,j,k,i,T;
	cin>>n;
	for (i=0;i<n;i++)
	cin>>a[i];
	
	sort(a,a+n);
	
	int ans=0;
	for (i=0;i<n;i++)
	{
		if ((i+1) %2==0)
		ans+= (a[i]-a[i-1]) ;
	}
	cout<<ans<<endl;
	
	return 0;
}