diff --git a/backup.py b/backup.py
index 32c0328..edcd38e 100644
--- a/backup.py
+++ b/backup.py
@@ -241,6 +241,7 @@ class DataBase:
         """)
 
         self.conn.row_factory = dict_factory
+        # self.conn.set_trace_callback(print)
 
         self.conn.commit()
 
@@ -272,9 +273,25 @@ class DataBase:
             try:
                 crypt_id_list.append(cursor.fetchone()['crypt_id'])
             except TypeError:
-                cursor.execute("""SELECT IFNULL(max(id) + 1, 0) as crypt_id FROM crypt""")
-                return cursor.fetchone()['crypt_id']
-        return most_frequent(crypt_id_list)
+                pass
+        try:
+            id = most_frequent(crypt_id_list)
+        except ValueError:
+            cursor.execute("""SELECT IFNULL(max(id) + 1, 0) as crypt_id FROM crypt""")
+            return cursor.fetchone()['crypt_id']
+        params = {'id': id,
+                  'name': ', '.join([f"'{file['name']}'" for file in list_file]),
+                  'path': ', '.join([f"'{file['path']}'" for file in list_file])}
+        cursor.execute("""SELECT 1 FROM files 
+        WHERE crypt_id={id}
+        AND name NOT IN ({name})
+        AND path NOT IN ({path})""".format(**params))
+        neighbour = cursor.fetchall()
+        if len(neighbour) > 0:
+            cursor.execute("""SELECT IFNULL(max(id) + 1, 0) as crypt_id FROM crypt""")
+            return cursor.fetchone()['crypt_id']
+        else:
+            return id
 
     def exist(self, file):
         cursor = self.conn.cursor()
@@ -313,7 +330,7 @@ class DataBase:
                 file_id += 1
                 proceed = True
         if proceed:
-            cursor.execute("""INSERT INTO crypt VALUES(?, ?)""", (crypt_id, compress_mode))
+            cursor.execute("""INSERT OR IGNORE INTO crypt VALUES(?, ?)""", (crypt_id, compress_mode))
             self.conn.commit()
             return str(crypt_id).zfill(ZFILL)
         else: