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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

class Program
{
	static void Main(string[] args)
	{
		// 整数の入力
	//	int a = int.Parse(Console.ReadLine());
		int a = 25;
		int b = 0;
		// スペース区切りの整数の入力

		// 文字列の入力
		//出力
		for (int i = 1; i <= a; i++)
		{
			for (int j = 1; j <=a ; j++)
			{
				int i1 = i % 10;
				string i2 = i.ToString().Substring(0, 1);
				int i3 = int.Parse(i2);
				int j1 = j % 10;
				string j2 = j.ToString().Substring(0, 1);
				int j3 = int.Parse(j2);
				if (i1==j3&&i3==j1)
				{
					b++;
				}
			}
		}
		Console.WriteLine(b);
	}
}