%!PS
/Courier             % name the desired font
20 selectfont        % choose the size in points and establish
                     % the font as the current one

% init random number generator
(%Calendar%) currentdevparams /Second get srand

1000000				% iteration count
0 0				% 0 wins on first selection 0 wins on switch
2 index				% get iteration count
{
rand 3 mod			% winning door
rand 3 mod			% first choice
eq {
	1 add
}
{
	exch 1 add exch
} ifelse
} repeat

% compute percentages
2 index div 100 mul exch 2 index div 100 mul


% display result
70 600 moveto
(Switching the door: ) show
80 string cvs show (%) show
70 700 moveto
(Keeping the same: ) show
80 string cvs show (%) show


showpage             % print all on the page