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F. Erasing Substrings

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputYou 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.

Input

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

Output

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

Examples

Input

adcbca

Output

aba

Input

abacabadabacaba

Output

aabacaba

Note

Possible operations in examples:

- adcbca adcba aba;
- abacabadabacaba abcabadabacaba aabadabacaba aabacaba.

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