INF = 1i64 << 60
n = read_line.to_i
a = read_line.split.map(&.to_i64)
dp = [-INF, -INF]
n.times do |i|
  if dp[0] == -INF && dp[1] == -INF
    dp[0] = -a[i]
  elsif dp[1] == -INF
    dp[0], dp[1] = {dp[0], -a[i]}.max, dp[0] + a[i]
  else
    dp[0], dp[1] = {dp[0], dp[1] - a[i], -a[i]}.max, {dp[1], dp[0] + a[i]}.max
  end
end
puts dp.max