diff --git a/latex/arrays.tex b/latex/arrays.tex
old mode 100644
new mode 100755
index 21f30a41..3e8d3c79
--- a/latex/arrays.tex
+++ b/latex/arrays.tex
@@ -1057,7 +1057,7 @@ \section{Discussion and Exercises}
 \begin{exc}
   Implement a method #rotate(a,r)# that ``rotates'' the array #a#
   so that #a[i]# moves to $#a#[(#i#+#r#)\bmod #a.length#]$, for all
-  $#i#\in\{0,\ldots,#a.length#\}$.
+  $#i#\in\{0,\ldots,#a.length-1#\}$.
 \end{exc}
 
 \begin{exc}