/*
TASK: ots
LANG: C++
*/
#include <iostream>
#include <limits.h>
using namespace std;

struct st
{
       int s;
       int v;
} B[1000000];

int sum;

bool cmp(st r, st e)
{
     return r.v>e.v;
}

int N;
int A[1000000];
int X[1000000];

int main()
{
    cin>>N;
    for(int i=0; i<N; i++)
    {
            cin>>A[i];
            if(i>0) {B[i-1].v = A[i] - A[i-1]; B[i-1].s = i-1;}
    }
    sort(A, A+N);
    sort(B, B+N-1, cmp);
    X[0] = 1;
    X[N-1] = 1;
    for(int h=0; h<N-1; h++)
    {
            int r = B[h].s;
            if(X[r]<1&&X[r+1]<1) {X[r]++; X[r+1]++; sum-=A[r+1]-A[r];}
    }
    cout<<sum+(A[N-1]-A[0])<<'\n';
    return 0;
}
