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++14 (GCC 5.4.1) (judge verdict: Accepted)

/*
  AUTHOR:SOURABH
  CREATED:19:01:20
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ordered_set tree<ll , null_type, less< ll >, rb_tree_tag, tree_order_statistics_node_update>
#define ll long long int
#define ld long double
#define fi first
#define se second
#define pb push_back
#define pob pop_back
#define W while
#define fn(i,x) for(i=0;i<x;i++)
#define fs(i,s,x) for(i=s;i<x;i++)
#define fr(i,x) for(i=x;i>=0;i--)
#define fit(it,s) for(it=s.begin();it!=s.end();it++)
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vii vector<int>
#define vll vector<ll>
#define mii map<int,int>
#define mll map<ll,ll>
#define mod 1000000007
#define MAX 100005
#define M 32

using namespace std;
using namespace __gnu_pbds;

ll c[10][10];

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    //freopen("in.txt","r",stdin);
    //freopen(2 "out.txt","w",stdout);

    ll n,i,j,s,e,ans=0;
    cin>>n;
    fs(i,1,n+1)
    {
        e=i%10;
        j=i;
        W(j)
        {
            s=j;
            j/=10;
        }
        c[s][e]++;
    }
    fn(i,10)
    {
        fn(j,10)
        ans+=c[i][j]*c[j][i];
    }
    cout<<ans;
}