Derek really likes string manipulations, but he is having trouble finding the index of a certain character in his string.

He wants to find the ~N_{th}~ occurrence of the ~K_{th}~ character.

Output the index of that character.

Input Specification

The first line will contain the two integers, ~N~ ~(1 \le N\le 10^5)~ and ~K~ ~(0 \le K\le 10^5-1)~.

The second line will contain a string of length ~\le10^5~ lowercase, latin characters.

It is guaranteed that the ~K_{th}~ character will appear at least ~N~ times.

Output Specification

On the first line, output the zero-based index of the ~N_{th}~ occurrence of the ~K_{th}~ character in the string.

Sample Input 1

1 2
abca

Sample Output 1

2

Sample Input 2

5 1
ababbbbbbbbbb

Sample Output 2

6