''' 

	An example of exception handling in Python. Read through it
	carefully and figure out what it will do when run from the command
	line with 1 as its argument, ang again with 0 as argument.  Pay
	special attention to which Entering/exiting messages get printed. 
	Then try it.
	
'''

import sys

def A(x):
    print "Entering A with", x
    result = B(2*x)
    print "Exiting A with", result
    return result

def B(x):
    print "  Entering B with", x
    result = C(3*x)
    print "  Exiting B with", result
    return result

def C(x):
    print "    Entering C with", x
    result = 1/x
    print "    Exiting C with", result
    return result

print "\nAnd (drum roll, please) the answer is..."
answer = A(int(sys.argv[1]))
print  answer, "!\n"