---

a = int(input())
l = 0
r = 0
p = 0
for i in range(a):
    n = int(input())
    if n > 0 and p > 0:
        r += abs(n)
        l += abs(p)
    elif n < 0 and p < 0:
        l += abs(n)
        r += abs(p)
    elif n < 0:
        l += abs(n)
    else:
        r += abs(n)
    p = n
    
print(max(l, r))