Single Occurrence Characters

Given a string \( s \), count the number of distinct characters in \( s \) that appear exactly once. In other words, for each character \( c \) in \( s \), if its frequency \( f(c) = 1 \), then it is counted toward the final answer.

For example, if \( s = \text{'hello'} \), the characters \( h, e, o \) appear only once, so the answer is 3.

inputFormat

The input is given via standard input (stdin) as a single line containing the string \( s \). The string may include spaces or special characters.

outputFormat

Output a single integer to standard output (stdout): the number of distinct characters in \( s \) that appear exactly once.

hello

3