Description: You are given a string s, initially consisting of n lowercase Latin letters. After that, you perform k operations with it, where $$k = \left\lfloor \log_2(n) \right\rfloor$$. During i-th operation you must erase some substring of length exactly 2i - 1 from s. Print the lexicographically minimal string you may obtain after performing k such operations. Input Format: The only line contains one string s consisting of n lowercase Latin letters (1 ≤ n ≤ 5000). Output Format: Print the lexicographically minimal string you may obtain after performing k operations. Note: Possible operations in examples: 1. adcbca $$\rightarrow$$ adcba $$\rightarrow$$ aba; 2. abacabadabacaba $$\rightarrow$$ abcabadabacaba $$\rightarrow$$ aabadabacaba $$\rightarrow$$ aabacaba.