n = read_line.to_i
a = read_line.split.map(&.to_i64)
dp = [-1i64 << 50, 0i64]
n.times do |i|
  dp[0], dp[1] = {dp[0], dp[1] - a[i]}.max, {dp[1], dp[0] + a[i]}.max
end
puts dp.max