You are given a string s, initially consisting of n lowercase Latin letters. After that, you perform k operations with it, where . During i-th operation you must erase some substring of length exactly 2^i - 1 from s.

Print the lexicographically minimal string you may obtain after performing k such operations.

The only line contains one string s consisting of n lowercase Latin letters (1 ≤ n ≤ 5000).

Print the lexicographically minimal string you may obtain after performing k operations.