text: # The guess API is already defined for you.
  # @param num, your guess
  # @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
  # def guess(num):
  
  class Solution(object):
      def guessNumber(self, n):
          """
          :type n: int
          :rtype: int
          """
          # binary search
          begin, end = 1, n
          while begin <= end:
              mid = (begin + end) / 2
              res = guess(mid)
              if res == 0:
                  return mid
              elif res > 0:
                  begin = mid + 1
              else:
                  end = mid - 1