B. Teams Forming

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

6
5 10 2 3 14 5

output

5

input

2
1 100

output

99

题意：n个学生两两组成小队，尽可能使组成小队的两人刷题数差距较小，求总最小刷题数。

贪心算法

代码：

#include<iostream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cstdio>
#include<cmath>
#include<set>
#include<map>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
#define mem(a,b) memset(a,b,sizeof(a))
#define closeio std::ios::sync_with_stdio(false)
 
int a[105];
 
int main()
{
	int n,i,s=0;
	cin>>n;
	for(i=0;i<n;i++)
		cin>>a[i];	
	sort(a,a+n);
	for(i=0;i<n;i+=2)
		s+=a[i+1]-a[i];
	cout<<s<<endl;
	return 0;
}