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Problems

Page numbering

Page numbering

Time limit 1 second
Memory limit 128 MiB

For numbering m pages in the book n digits were used. By given n output the corresponding m or 0 if there is no solution. Numbering starts from first page.

Input data

The only number n. The book contains no more than 7000 pages.

Output data

Print the number of pages in the book.

Examples

Input example #1
27
Output example #1
18