#!/usr/bin/env python
#
# Operation on Two Numbers
#
# Yotam Medini <yotam.medini@gmail.com>
# 2009/November/06

import sys

if len(sys.argv) != 1 + 3:
    sys.stderr.write("Usage: %s <operation> <number1> <number2>\n" %
                     sys.argv[0])
    sys.stderr.write("<operation> = one of: 'add', 'sub', 'mul', 'div', 'mod'\n")
    sys.exit(1)


op = sys.argv[1]  #  The operation name (string)
n1 = int(sys.argv[2]) # First integer number
n2 = int(sys.argv[3]) # Second integer number

result = None
if op == 'add':       # Add!       (addition, sum)
    result = n1 + n2  
if op == 'sub':       # Subtract!  (subtraction, difference)
    result = n1 - n2
if op == 'mul':       # Multiply!  (Multiplication, product)
    result = n1 * n2
if op == 'div':       # Divide!    (Division, quotient, ratio)
    if n2 == 0:
        sys.stderr.write("Cannot div by zero\n")
        sys.exit(1)
    result = n1 / n2
if op == 'mod':       # Get divison Residue!  (Modulo, Remainder)
    if n2 == 0:
        sys.stderr.write("Cannot mod by zero\n")
        sys.exit(1)
    result = n1 % n2
if result == None:
    sys.stderr.write("Unknwon operation: %s\n" % op)
    sys.exit(1)
    
sys.stdout.write("%d\n" % result)
sys.exit(0)