n = int(input())
a = list(map(int,input().split()))
if sum(a) < 0:
    a = [-1*i for i in a]
a.sort(reverse=True)
A = 0
B = 0
for i in range(n):
    if i%2:
        B += a[i]
    else:
        A += a[i]
print(abs(A)-abs(B))