#region Header
#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
from queue import PriorityQueue
import bisect
import heapq

def input():
    return sys.stdin.readline()[:-1]

sys.setrecursionlimit(1000000)
#endregion

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)



def main():
    N = int(input())
    Y = [-10**12] + sorted(list(map(int, input().split()))) + [10**12]

    i = 1
    v = 0
    prev = Y[0]
    while i < N+1:
        if Y[i] - prev < Y[i+1] - Y[i]:
            # 下の方が近い
            v += Y[i] - prev
            i += 1
        else:
            # 上の方が近い
            v += Y[i+1] - Y[i]
            prev = Y[i+1]
            i += 2
    print(v)

if __name__ == '__main__':
    main()