diff --git a/string/ac-automaton.cc b/string/ac-automaton.cc
index ecf9636..911f179 100644
--- a/string/ac-automaton.cc
+++ b/string/ac-automaton.cc
@@ -1,3 +1,5 @@
+// lg-5357.cc
+
 #include "../include.hh"
 
 void solve(vector<string> ss, string t) {