You are given a string of ‘n’ characters where n is even. The string only consist of 6 type of characters: (){}[]. The task is to form a well formed expression. A well formed expression consist of proper nesting of braces and their is no priority between the braces like [ > } > ). You can edit any bracket and change it to remaining types for accomplishing the task.

Example 

A. "(){}" is valid 

B. "({[]})” is valid 

C. “((})” is invalid