Finding the index of the character whose removal will make a palindrome
Code Style

As @coderodde also remarked, you should import specific classes.  Wildcard imports are for throw-away code and early development; no later than when your code is approaching completeness, you should replace any then-remaining wildcard imports with specific imports.  There are tools that can help you with that.

Also, format your code consistently.  Your indentation and placement of spaces are irregular.  I find code much easier to read when there are spaces on each side of every binary operator, but if you prefer not to use such spaces then at least be consistent!

I/O

For what it's worth, unlike @coderodde, I have no problem with BufferedReader for your input.  For input whose form is so simple, Scanner does not provide much advantage.

Performance

This is the main area of concern, and indeed I do not find it surprising that your code ...

        for(int i=0;i&lt;sb.length()&amp;&amp;flag==0;i++){
            StringBuffer s = new StringBuffer(sb);
            s.deleteCharAt(i);
            if(isPalindrom(s.toString())){
                System.out.println(i);
                break;
            }   
        }


... does not perform well.  Regardless of the details of the palindrome-checking algorithm, it is performing far more work than it needs to do when used this way.  In particular, it is very wasteful to test every deletion candidate, and it is slightly wasteful to test separately whether the full string is already a palindrome.  For each string it tests, your code may perform work proportional to the square of the length of the string.

Instead of testing every possible deletion, simply scan each test string from both ends until you find a pair of corresponding characters that differ.  If the string can be made a palindrome by deleting a single character, then that character will be one of those two.  They are the only candidates you need to consider.  By limiting yourself to considering only those as deletion candidates, the maximum amount work performed by your code is only linear in the length of the string.  (Also, if every corresponding pair of characters matches, then the string is already a palindrome, so you don't need to perform a separate check for that.)