First Non-Repeating Character

Given a string s, your task is to find and output the first non-repeating character in s. If there is no such character, output an empty string.

The problem can be modeled using the following concept:

For a character c in the string, determine its frequency \(f(c)\) and identify the first character for which \(f(c)=1\). If no character meets this criterion, output an empty string.

Examples:

• Input: "leetcode" → Output: "l"
• Input: "loveleetcode" → Output: "v"
• Input: "aabb" → Output: ""

inputFormat

Input is read from standard input (stdin) as a single line containing the string s. The string may include spaces and printable ASCII characters.

outputFormat

Output the first non-repeating character from the input string to standard output (stdout). If no such character exists, output an empty string.## sample

leetcode

l