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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        int n = Integer.parseInt( in.nextLine() );

        if( n < 10 ){
            System.out.println( n );
            return;
        }
        if( n < 100 ){
            int ans = 9;
            for( int i = 10 ; i <= n ; i++ ){
                if( i/10 == i%10 ){
                    ans+=3;
                    continue;
                }
                if( i % 10 == 0 ){
                    continue;
                }
                int rev = ( i % 10 ) * 10 + ( i / 10 );
                if( n < rev ){
                    continue;
                }
                ans++;
            }
            System.out.println( ans );
            return;
        }
        
        System.out.println( 0 );
        return;

    }

}