code = '+[,.]'

ip = p = 0
stack = mem = []

while true
  case code[ip]
  when '+'
    if mem[p] == nil
      mem[p] = 1
    else
      mem[p] += 1
    end

  when '-'
    if mem[p] == nil
      mem[p] = -1
    else
      mem[p] -= 1
    end

  when '>'
    p += 1

  when '<'
    p -= 1

  when '.'
    print mem[p].chr

  when ','
    STDOUT.flush

    input = gets.chomp[0]

    if input != nil
      mem[p] = input
    end

  when '['
    stack.push ip

  when ']'
    if mem[p] != 0
      ip = stack[-1]
    else
      stack.pop
    end
  end

  ip += 1

  if ip == code.length
    break
  end
end