Minimum Operations to Empty a String

Given a non-empty string s, in one operation you may remove all occurrences of any single character from s. Your task is to determine the minimum number of operations required to make the string empty. Essentially, in each operation you choose one character and remove every occurrence of that character from the current string.

Example: For the string "abac", the distinct characters are a, b, and c, thus the minimum number of operations is 3.

Note: The answer is equal to the number of unique characters in the string.

inputFormat

The input consists of a single line containing the string s.

Constraints: 1 ≤ |s| ≤ 10⁵.

outputFormat

Output a single integer representing the minimum number of operations required to remove all characters from the string.

abac

3