#!/usr/bin/env python

def mul():
    import json
    import sys

    in_file = sys.argv[1]
    out_file = sys.argv[2]

    with open(in_file) as f:
        in_dict = json.load(f)

    out_dict = {'product': in_dict['x1'] * in_dict['x2']}

    with open(out_file, 'w') as f:
        json.dump(out_dict, f)
