diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4613a62
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+Usage:
+
+`./odds.py [num_dice [sides_on_dice [monte_carlo_runs]]] [debug] [no_mc] [simple]`

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4613a62
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+Usage:
+
+`./odds.py [num_dice [sides_on_dice [monte_carlo_runs]]] [debug] [no_mc] [simple]`
diff --git a/odds.py b/odds.py
index 6546045..6cc5c50 100755
--- a/odds.py
+++ b/odds.py
@@ -11,8 +11,10 @@
 
 success_odds_by_dice = {}
 
+sides = 6
+
 def get_odds(num_dice, indent = 0):
-  global debug, success_odds_by_dice
+  global sides, debug, success_odds_by_dice
   def iprint(val, *args):
     if debug:
       print (indent * " ") + str(val).format(*args)
@@ -27,14 +29,14 @@
 
   total_odds_success = 0
 
-  num_rolls = pow(6, num_dice)
+  num_rolls = pow(sides, num_dice)
   iprint("num rolls with {} dice: {:,}", num_dice, num_rolls)
   for i in xrange(1, num_dice + 1):
     remaining_dice = num_dice - i
-    num_rolls_with_i_sixes = pow(5, remaining_dice) * fact(num_dice) / (fact(remaining_dice) * fact(i))
+    num_rolls_with_i_sixes = pow(sides - 1, remaining_dice) * fact(num_dice) / (fact(remaining_dice) * fact(i))
     for j in xrange(i + 1, num_dice + 1):
       num_rolls_with_i_sixes 
-    iprint(" num rolls of {} dice with {} six(es): {:,}", num_dice, i, num_rolls_with_i_sixes)
+    iprint(" num rolls of {} dice with {} {}'s: {:,}", num_dice, i, sides, num_rolls_with_i_sixes)
     odds_i_sixes = num_rolls_with_i_sixes / float(num_rolls)
     iprint("  odds of that happening: {}", odds_i_sixes)
     total_odds_success += get_odds(num_dice - i, indent + 3) * odds_i_sixes
@@ -52,7 +54,7 @@
     while dice_left > 0:
       num_sixes = 0
       for j in xrange(0, dice_left):
-        if random.randint(1, 6) == 6:
+        if random.randint(1, sides) == sides:
           num_sixes += 1
       if num_sixes == 0:
         dice_left = 0
@@ -75,21 +77,26 @@
 do_monte_carlo = not simple_output and not find_flag("no_mc")
 
 dice = int(sys.argv[1])
-odds = get_odds(dice)
-monte_carlo_iters = 100000
+
 if len(sys.argv) > 2:
-  monte_carlo_iters = int(sys.argv[2])
+  sides = int(sys.argv[2])
+
+monte_carlo_iters = 100000
+if len(sys.argv) > 3:
+  monte_carlo_iters = int(sys.argv[3])
 
 if do_monte_carlo:
   monte_carlo_odds = get_monte_carlo_odds(monte_carlo_iters, dice)
 
+odds = get_odds(dice)
+
 if debug:
   # extra line to separate debug output
   print
 if simple_output:
   print odds
 else:
-  odds_str = "odds of getting donuts with {} dice: {:.2}%".format(dice, odds * 100)
+  odds_str = "odds of getting donuts with {} {}-sided dice: {:.2}%".format(dice, sides, odds * 100)
   if do_monte_carlo:
     odds_str += ", monte carlo with {:,} iterations gives: {:.2}%".format(monte_carlo_iters, monte_carlo_odds * 100)
   print odds_str