Problem Statement

Pair Outer Characters Given a non-empty string `s` of lowercase English letters, construct a new string by repeatedly taking the leftmost remaining character followed by the rightmost remaining character. Continue moving inward. If one middle character remains, append it at the end. Input Format The only line contains the string `s`. Output Format Print the constructed string. Constraints `1 <= |s| <= 200000`. Examples Input: `abcdef` Output: `afbecd` Input: `abcde` Output: `aebdc` Notes For an odd-length string, its middle character is appended after every outer pair. Characters are paired by their original positions.