#
# Kingston 1.11
#

true, false = 1,0

def binary_search(a,b,x):

  while not (a > b):

    mid = (a+b) / 2

    if x == entries[mid]:
      return true
    
    elif x < entries[mid]:
      b = mid - 1

    else:
      a = mid + 1

  return false