diff --git a/chapter04.tex b/chapter04.tex
index 6e81d9c..9ae6bdc 100644
--- a/chapter04.tex
+++ b/chapter04.tex
@@ -714,7 +714,7 @@ that both contain $n$ elements.
 Our task is to calculate the number of elements
 that belong to both of the lists.
 For example, for the lists
-\[A = [5,2,8,9,4] \hspace{10px} \textrm{and} \hspace{10px} B = [3,2,9,5],\]
+\[A = [5,2,8,9] \hspace{10px} \textrm{and} \hspace{10px} B = [3,2,9,5],\]
 the answer is 3 because the numbers 2, 5
 and 9 belong to both of the lists.