Contest Duration: - (local time) (100 minutes) Back to Home
C - Doubled /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

• x の十進表記 (先頭に 0 を付けない) は偶数桁であり、その前半と後半は文字列として等しい。

### 制約

• N は整数
• 1 ≤ N < 10^{12}

### 入力

N


### 入力例 1

33


### 出力例 1

3


11, 22, 333 個が条件を満たします。

### 入力例 2

1333


### 出力例 2

13


### 入力例 3

10000000


### 出力例 3

999


Score : 300 points

### 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.

### Constraints

• N is an integer.
• 1 ≤ N < 10^{12}

### Input

Input is given from Standard Input in the following format:

N


### 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