def read_data
  $stdin.read.lines(chomp: true).drop(1)
end

def ok?(prev, value)
  if prev
    prev[-1] <= value[0]
  else
    true
  end
end

def solve(n, list, used, acc, max)
  if max.join.size < acc.join.size
    max = acc
  end
  list.each_with_index do |v, i|
    unless used[i]
      if ok?(acc.last, v)
        used[i] = true
        val = solve(n + 1, list, used, acc + [v], max)
        if max.join.size < val.join.size
          max = val
        end
        used[i] = false
      end
    end
  end
  max
end

def remove_error_data(list)
  list.find_all do |v|
    if v.size == 1
      true
    else
      v.chars.each_cons(2).all? do |a, b|
        a.codepoints.first <= b.codepoints.first
      end
    end
  end
end

def main
  list = read_data
  valid_list = remove_error_data(list)
  pattern = solve(0, valid_list, [false] * valid_list.size, [], [])
  puts pattern.join.size
end

main