diff --git a/app/common.php b/app/common.php
index 3a0efff..b4e0dce 100644
--- a/app/common.php
+++ b/app/common.php
@@ -62,7 +62,7 @@ function checkToken($token): array
  */
 function generate_random_str(int $length = 8): string
 {
-    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
+    $characters = '0123456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXY';
     $str = '';
 
     $maxIndex = strlen($characters) - 1;