import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
#input = sys.stdin.readline
n = int(input())
alist = list(map(int,input().split()))
#alist = []
#s = input()
#n,m = map(int,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
x = 0
y = 0
t = 0
a = []
b = []
for i in alist:
    if i > 0:
        a.append(i)
    elif i < 0:
        b.append(-i)
a.sort()
b.sort()
a = collections.deque(a)
b = collections.deque(b)
for i in range(n):
    if len(a) >= 1 and len(b) >= 1:
        if t == 0:
            x += a.pop()
        else:
            y += b.pop()
    elif a:
        if t == 0:
            x += a.pop()
        else:
            y -= a.popleft()
    elif b:
        if t == 0:
            x -= b.popleft()
        else:
            y += b.pop()
    else:
        break
    t ^= 1

print(x-y)