Problem:
Score : 200 points

Problem Statement

Given is an integer N. Find the number of positive integers less than or equal to N that have an odd number of digits (in base ten without leading zeros).

Constraints

1 \leq N \leq 10^5

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of positive integers less than or equal to N that have an odd number of digits.

Sample Input 1

11

Sample Output 1

9

Among the positive integers less than or equal to 11, nine integers have an odd number of digits: 1, 2, \ldots, 9.

Sample Input 2

136

Sample Output 2

46

In addition to 1, 2, \ldots, 9, another 37 integers also have an odd number of digits: 100, 101, \ldots, 136.

Sample Input 3

100000

Sample Output 3

90909

Solution in JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input) {
    var N = input;
    var length = N.length;
    if(length % 2 == 0){
        console.log((length - 1) * 9) 
    }else{
        var _N = N;
        var a = (length - 2) * 9
        var b = _N.slice(1);
        console.log(parseInt(b,10) + a + 1);
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));