/* -*- coding: utf-8 -*-
 *
 * 3066.cc:  No.3066 Collecting Coins Speedrun 1 - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

/* global variables */

int cs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", cs + i);

  int c0 = min(cs[0], 0), c1 = max(cs[n - 1], 0);
  int l = (c1 - c0) * 2;

  printf("%d\n", l);

  return 0;
}