18. The apparatus of claim 17 , wherein the incorrect input type comprises any one of an incorrect input due to a continuous key press, an incorrect input due to an adjacent key press, an incorrect input due to a key omission, and an incorrect input due to key input order.
17. The apparatus of claim 15 , wherein the controller is configured to: determine the cost of the insert operation, delete operation, and replace operation corresponding to the identified keypad type by identifying at least one or more incorrect input types of high frequency of occurrence in the identified keypad type and, if operating conditions of at least one or more incorrect input types having the high frequency of occurrence are met, determining the cost of the insert operation, the delete operation or the replace operation as a first value and otherwise, determine the cost of the insert operation, the delete operation or the replace operation as a second value higher than the first value, and determine the cost of the insert operation, the delete operation or the replace operation as a basic cost whether the operating conditions are met or not.