N = gets.to_i
A = gets.split.map(&:to_i)

R = A.each_slice(2).map { |a, b| a - b }
L = A.each_slice(2).map { |a, b| b - a }

SUM_R = [0]
SUM_L = [0]

R.inject(0) { |s, r| 
  v = s + r
  SUM_R << v
  v
}

L.reverse.inject(0) { |s, l|
  v = s + l
  SUM_L.unshift(v)
  v
}

ans = -Float::INFINITY

0.upto(N) do |i|
  v = SUM_L[i] + SUM_R[i]

  ans = v if ans < v
end

puts ans