N = int(input())
A = list(map(int, input().split()))

if N == 1:
  print(-A[0])
  exit()

dp = [0, -A[0]]

for i in range(1, N):
  ndp = [max(dp[1] + A[i], dp[0]), max(dp[0] - A[i], dp[1])]
  dp = ndp

print(max(dp))