sequence

def check(arr)
  counter = 0
  
  arr.each do |key|
    if key == '('
      counter += 1  
    else
      counter -= 1
    end
  end
  
  if (counter < 0 || counter > 0)
    return false
  else
    return true
  end
  
end

seq = '(()())'.split('')

puts check(seq)