#!/usr/bin/python
#                 Sanjoy Mahajan and David MacKay
# python/examples/commandline2.py
#
Usage = """
A python program to sum the integers from 1 to n,
where n is given on the command line.

$ commandline2.py 15
120

To make this file executable,
$ chmod +x commandline2.py
"""
import sys
total = 0
if (len(sys.argv)<2):
    print "error - usage:\n $ commandline2.py <number>"
else:
    for i in range(int(sys.argv[1])+1):
        total += i
    print total

print """
The int function converts the string sys.argv[1]
to an integer.
Notice the +1 in the range function.
"""