Vasya's arithmetic#2063
Father once gave Vasya the following task: Find the sum of all digits of the numbers from to 10^n. Vasya, who, in addition to mathematics, was interested in programming, quickly solved the problem. But now Vasya's father has a new problem—how to check whether his son's answer is correct?
Help Vasya's father solve this problem, as he feels awkward not being able to verify his son's answer.
A single line contains a non-negative integer 10^n. It is known that the length of the number does not exceed 10^7 + 1.
A single integer: the required sum of digits.
Exemple 1