#!/usr/bin/env python3
import argparse
# create parser
parser = argparse.ArgumentParser(
         description='add or substract command line arguments',
         epilog = 'please report comments/bugs to arlotto@univ-tln.fr')

#position 1
parser.add_argument('a', type = float)

#position 2
parser.add_argument('b', type = float)

# add option 
parser.add_argument('-s','--substract', action='store_true',
                    help='substract b from a')


args = parser.parse_args()

a = args.a
b = args.b

if args.substract == False :
    res = a + b
else :
    res = a - b
    
print(res)