def checkInput(type_string, present_value, low, high):
    '''uses a while loop, loops until an acceptible answer is given, then returns it'''
    prompt = "Present %s is %d, enter a new value (%d-%d): " % (type_string, present_value, low, high)
    while True: 
       try:
          a = int(raw_input(prompt))
          if low <= a <= high:
             return a
       except ValueError:
          print "Enter an integer number, please!"


# modify the present strength of 10 within the range (1-18)
modified_strength = checkInput("strength", 10, 1, 18)
print modified_strength