Update exam/packet.tex

exam/packet.tex

@@ -156,7 +156,7 @@ You are given a string S composed of only the characters ‘6’, ‘7’, 'A’
 \inputformat
 \begin{itemize}
     \item The first line consists of the string S. The string consists only of the characters 6, 7, A, B, and #.
-    \item $|S|$ ($1 \leq n \leq 10^5$), the number of intervals.
+    \item \texttt{s} ($1 \leq |s| \leq 10^5$)
 \end{itemize}
 
 \outputformat