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.io.*;
public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader((new InputStreamReader(System.in)));
        int N = Integer.parseInt(reader.readLine());
        long res = 0;
        int[][] a = new int[10][10];
        for(int i=1;i<N;i++){
            String s = Integer.toString(i);
            a[Character.getNumericValue(s.charAt(0))][i%10]+=1;
        }

        for(int u=0;u<10;u++){
            res+=a[u][u];
            for(int i=u+1;i<10;i++){
                res+=2*a[u][i]*a[i][u];
            }
        }
        System.out.println(res);
    }

}