Polycarpus loves lucky numbers. Everybody knows that lucky numbers are positive integers, whose decimal representation (without leading zeroes) contain only the lucky digits *x* and *y*. For example, if *x* = 4, and *y* = 7, then numbers 47, 744, 4 are lucky.

Let's call a positive integer *a* undoubtedly lucky, if there are such digits *x* and *y* (0 ≤ *x*, *y* ≤ 9), that the decimal representation of number *a* (without leading zeroes) contains only digits *x* and *y*.

Polycarpus has integer *n*. He wants to know how many positive integers that do not exceed *n*, are undoubtedly lucky. Help him, count this number.
The first line contains a single integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">9</sup>) — Polycarpus's number.
#!/usr/bin/python3.6
# -*- coding: utf-8 -*-
# @Time    : 2020/12/4 1:44 PM
# @Author  : Songtao Li
s = set()


def DFS(x, y, num, max_n):
    s.add(num)
    num_x = 10 * num + x
    num_y = 10 * num + y
    if num_x and num_x <= max_n:
        DFS(x, y, num_x, max_n)
    if num_y and num_y <= max_n:
        DFS(x, y, num_y, max_n)


if __name__ == "__main__":
    n = int(input())
    for i in range(10):
        for j in range(i, 10):
            DFS(i, j, 0, n)
    print(len(s)-1)
