How to revoke all privilege to root

Question

Unfortunately, I lock all privilege to root user. I dont know how to revoke. Please anyone help me to revoke all privilege to root user.

I tried below query but everything says access denied.

mysql> FLUSH PRIVILEGES;
ERROR 1227 (42000): Access denied; you need (at least one of) the RELOAD privilege(s) for this operation
mysql> SELECT user();
+----------------+
| user()         |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

mysql> SELECT current_user();
+----------------+
| current_user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'root'@'localhost';
+--------------------------------------------------------------------------+
| Grants for root@localhost                                                |
+--------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'root'@'localhost' IDENTIFIED BY PASSWORD <secret> |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION             |
+--------------------------------------------------------------------------+
2 rows in set (0.00 sec)

Please anyone help me..

Thanks in advance