Problems
Vasya`s arithmetic
Vasya`s arithmetic
Father once slipped Vasya's task: find the sum of all digits of numbers from 1 to 10^n. Vasya, who was fond of mathematics but also in programming, quickly solved the puzzle, but with Vasya's father is now a problem - and how to check the correctness of the answer son?
Help dad Vasya's solve this puzzle, and then he somehow embarrassed in front of her son because of the inability to verify the answer with his son.
Input data
In single line set to one non-negative integer - 10^n. It is known that the length of no more than a 10^7+1.
Output data
A single number - the required amount of digits.
Examples
Input example #1
100
Output example #1
901