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 Ruby (2.3.3) (judge verdict: Accepted)

n = gets.to_i

def pair(x)
  a = x%10
  while x!=0
    b = x
    x /= 10
  end
  return [a, b]
end

freq = {}

(1..n).each do |i|
  p = pair(i)
  freq[p] = 0 if !freq.has_key?(p)
  freq[p] += 1
end

ans = 0

(1..n).each do |i|
  p = pair(i)
  q = [p[1], p[0]]
  ans += freq[q] if freq.has_key?(q)
end

puts ans