Problem Statement

Given is an integer N.
How many integers x between 1 and N (inclusive) satisfy the following condition?

• The decimal representation (without leading zeros) of x has an even number of digits, and its first and second halves are equal as strings.

Input

Input is given from Standard Input in the following format:
N

Output

Print the answer.

Constraints

• N is an integer.
• 1 ≤ N < 10^{12}

Sample Input 1

33

Sample Output 1

3

Three numbers 11, 22, and 33 satisfy the condition.

Sample Input 2

1333

Sample Output 2

13

For example, the decimal representation of 1313 has four digits, and its first and second halves are both 13, so 1313 satisfies the condition.

Sample Input 3

10000000

Sample Output 3

999

见题面 Input 部分

见题面 Output 部分