#Conversion from binary.
#The input is a string of 0's and 1's.
#The return value is either an
#integer (the number represented
#by the binary string) or "ERROR"

def convert_from_binary(s):
  val=0
  err=0
  for bit in s:
    if bit=='0':
      val=2*val
    elif bit =='1':
      val=2*val+1
    else:
      err=1
  if err:
    return "ERROR"
  else:
    return val

#A simple test of the program
def test_convert():
  s=raw_input("Enter string in binary")
  result=convert_from_binary(s)
  if result=="ERROR":
    msg="The input was not a valid binary number."
  else:
    msg="The input is the binary representation of "+str(result)
  showInformation(msg)

#This allows us to convert a bunch of strings, until we're tired.
def better_test_convert():
  s=raw_input("Enter string in binary, or 'QUIT' to quit")
  result=convert_from_binary(s)
  while result!="ERROR":
    msg="The input is the binary representation of "+str(result)
    showInformation(msg)
    s=raw_input("Enter string in binary, or 'QUIT' to quit")
    result=convert_from_binary(s)
  print len(result)
  if s=="QUIT":
    showInformation("Goodbye")
  else:
    showInformation("Illegal input. Program terminating.")