diff --git "a/9\354\236\245/\354\240\204\355\231\224\353\262\210\355\230\270\353\252\251\353\241\235.java" "b/9\354\236\245/\354\240\204\355\231\224\353\262\210\355\230\270\353\252\251\353\241\235.java"
index 22fc385..18cc76b 100644
--- "a/9\354\236\245/\354\240\204\355\231\224\353\262\210\355\230\270\353\252\251\353\241\235.java"
+++ "b/9\354\236\245/\354\240\204\355\231\224\353\262\210\355\230\270\353\252\251\353\241\235.java"
@@ -4,20 +4,24 @@
 
 public class Solution {
     public boolean solution(String[] phoneBook) {
-        Set<String> prefixes = new HashSet<>();
+        Set<String> phoneNumbers = new HashSet<>();
+
+        phoneBook = Arrays.stream(phoneBook)
+                .sorted((p1, p2) -> {
+                    return p1.length() - p2.length();
+                })
+                .toArray(String[]::new);
 
         for (String phone : phoneBook) {
             for (int end = 1; end < phone.length(); end++) {
-                prefixes.add(phone.substring(0, end));
-            }
-        }
+                String prefix = phone.substring(0, end);
 
-        for (String phone : phoneBook) {
-            if (prefixes.contains(phone)) {
-                return false;
+                if(phoneNumbers.contains(prefix)) return false;
             }
+
+            phoneNumbers.add(phone);
         }
 
         return true;
     }
-}
+}
\ No newline at end of file