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.
n = int(input())
res = set()

def solve(p, l):
    if p > n or l > 10:
        return
    if p > 0:
        res.add(p)
    solve(p * 10 + a, l + 1)
    solve(p * 10 + b, l + 1)

for a in range(0, 10):
    for b in range(0, a):
        solve(0, 0)
print(len(res))
