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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
int main(void) {
    long n, i, j;
    long ans;
    char a[7];
    char b[7];
    scanf("%ld", &n);
    ans=0;
    for (i=1; i<=n; i++) {
        sprintf(a, "%ld", i);
        for (j=0; j<n; j++) {
            sprintf(b, "%ld", j);
            if (a[0] == b[strlen(b)-1]) {
                if (a[strlen(a)-1] == b[0]) {
                    ans++;
                }
            }
        }
    }
    printf("%ld", ans);
    return 0;
}