N = int(input())
A = list(map(int, input().split()))
INF = float('inf')
s = [0, -INF, -INF, -INF]
f = 0
for a in A:
  ns = s[:]
  if s[2] >= s[0]:f=1
  ns[0] = max(s[0], s[2])
  ns[1] = max(s[1], s[3])
  ns[2] = max(s[1]+a, s[3]+a)
  ns[3] = max(s[0]-a, s[2]-a)
  s = ns

ans = max(s) if f else max(s[1:])
print(ans)