diff --git a/chapter_02/coin_flips.py b/chapter_02/coin_flips.py
index 7d08772..3c0a0c4 100644
--- a/chapter_02/coin_flips.py
+++ b/chapter_02/coin_flips.py
@@ -12,7 +12,7 @@
 import numpy as np
 
 N = 1000000
-M = 4
+M = 3
 
 heads = np.zeros(M+1)