Changes to be committed:
	new file:   12-1.rst
	new file:   12-1_random_walk_d1.aux
	new file:   12-1_random_walk_d1.dvi
	new file:   12-1_random_walk_d1.pdf
	new file:   12-1_random_walk_d1.py
	new file:   12-1_random_walk_d1.tex
	new file:   12-1_random_walk_d1.tex.backup
    new file:   before.txt
	new file:   figure_1.pdf
	new file:   figure_1.png
	new file:   figure_1.xbb