Given a set-like list of lowercase letters inside braces, count how many distinct letters appear.
Problem
You are given a string that represents a collection of lowercase Latin letters inside curly braces, with commas separating the letters. Your task is to determine how many different letters appear in the collection.
The same letter may appear multiple times in the input, but it should be counted only once.
Goal
Return the number of unique lowercase letters present in the string.
Input Format
- A single line containing a string in the form
{a, b, c}. - The string contains lowercase English letters, commas, spaces, and curly braces.
Output Format
- Print a single integer: the number of distinct lowercase letters in the input string.
Constraints
- The input consists only of lowercase English letters and separators.
- There is at least one letter in the collection.
- The exact official limits are not required for practice; the intended solution is linear in the string length.
Example 1
Input
{a, b, c}Output
3
Explanation
The distinct letters are a, b, and c.
Example 2
Input
{a, a, b, c, c}Output
3
Explanation
Repeated letters are counted once, so the distinct letters are a, b, and c.
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