def isIn(char, aStr):
    '''
    char: a single character
    aStr: an alphabetized string

    returns: True if char is in aStr; False otherwise
    '''
    # Your code here
    if len(aStr) <= 1 and aStr != char :
        return False
    elif aStr[len(aStr) / 2] == char :
        return True
    elif char < aStr[len(aStr) / 2] :
        return isIn(char, aStr[:len(aStr) / 2])
    else :
        return isIn(char, aStr[len(aStr) / 2:])