tyvj1294 小v的舞会

//贪心，取两头，怎么证明我不懂
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#define ll long long
using namespace std;
ll n,a[10005],b[10005],sum;
int main(){
    cin>>n;
    for(int i = 1;i <= n;i++) scanf("%lld",&a[i]);
    sort(a+1,a+1+n);
    int l = 1,r = n,opt = 0;
    for(int i = 1;i <= n;i++){
        if(!opt) b[i] = a[l++];
        else b[i] = a[r--];
        opt ^= 1;
    }
    b[0] = b[n];
    for(int i = 1;i <= n;i++){
        if(b[i] > b[i-1]) sum += b[i] - b[i-1];
        else sum += b[i-1] - b[i];
    }
    cout<<sum;
    return 0;
}