Score : 400 points
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:
Input is given from Standard Input in the following format:
N
Print the answer.
25
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).
1
1
100
108
2020
40812
200000
400000008