Problem:
Score : 400 points

Problem Statement

Given is a positive integer N.

Find the number of pairs (A, B) of positive integers not greater than N that satisfy the following condition:

When A and B are written in base ten without leading zeros, the last digit of A is equal to the first digit of B, and the first digit of A is equal to the last digit of B.

Constraints

1 \leq N \leq 2 \times 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

25

Sample Output 1

17

The following 17 pairs satisfy the condition: (1,1), (1,11), (2,2), (2,22), (3,3), (4,4), (5,5), (6,6), (7,7), (8,8), (9,9), (11,1), (11,11), (12,21), (21,12), (22,2), and (22,22).

Sample Input 2

1

Sample Output 2

1

Sample Input 3

100

Sample Output 3

108

Sample Input 4

2020

Sample Output 4

40812

Sample Input 5

200000

Sample Output 5

400000008

Solution in PHP7 (7.0.15) (judge verdict: Accepted)

<?php

 $n = trim(fgets(STDIN));
 
 $cnt = [];
 
 for($i=1;$i<=$n;$i++){
   if($i%10==0){
     continue;
   }
   $s = substr($i, 0, 1);
   $e = substr($i, -1);
   if(!isset($cnt[$s.$e])){
      $cnt[$s.$e]=0;
   }
   $cnt[$s.$e]++;
 }
 
 $ans=0;
 foreach($cnt as $key => $val){
//   echo $key." ".$val.PHP_EOL;
   if(isset($cnt[strrev($key)])){
     $ans+=$val*$cnt[strrev($key)];
   }
 }
 
 echo $ans;