N = gets.to_i
A = gets.split.map(&:to_i)
ans = (1..100).map {|m|
  p, q = (1..199).zip(A).map {|i, a|
    [m - (m - i).abs, 0].max - a.to_i
  }.inject([0, 0]) {|(p, q), x|
    [p + [0, x].max, q - [0, x].min]
  }
  if q >= p
    q
  else
    Float::INFINITY
  end
}.min
puts ans