Please give the solution appropriately. Previous code is not working Dear.

use only C program.

Problem Statement

You are given a string S of small letters. Count the total unique characters from the string and print them.

Note: Here unique means that occured exactly once.

Input Format

The first line of the input will contain a positive integer N. (Length of the string)

The second line will contain a string S, consisting of small letters(a-z)

Constraints

0 < N <= 100

a <= S[i] <=z

Output Format

Print the total number of unique characters.

Sample Input 0

12 iuuasdbddqzu 

Sample Output 0

6 

Sample Input 1

10 acckyppomp 

Sample Output 1

5