One beautiful July morning a terrible thing happened in Mainframe: a mean virus Megabyte somehow got access to the memory of his not less mean sister Hexadecimal. He loaded there a huge amount of *n* different natural numbers from 1 to *n* to obtain total control over her energy.

But his plan failed. The reason for this was very simple: Hexadecimal didn't perceive any information, apart from numbers written in binary format. This means that if a number in a decimal representation contained characters apart from 0 and 1, it was not stored in the memory. Now Megabyte wants to know, how many numbers were loaded successfully.
Input data contains the only number *n* (1 ≤ *n* ≤ 10<sup class="upper-index">9</sup>).
For *n* = 10 the answer includes numbers 1 and 10.
10
2
20
3
72
3
99
3
100
4
101
5
102
5
111
7
112
7
745
7
23536
31
1
1
1010011
83
312410141
511
1000000000
512
999999999
511
111111111
511
101010101
341
121212121
511
106341103
383
901556123
511
832513432
511
3
1
732875234
511
7
1
9
1
2
1
11
3
12
3
13
3
101020101
351
111100100
484
110110101
437
100111001
313
100100
36
110100102
421
# https://codeforces.com/problemset/problem/9/C

import sys
import math


def main():
    # sys.stdin = open('E:\\Sublime\\in.txt', 'r')
    # sys.stdout = open('E:\\Sublime\\out.txt', 'w')
    # sys.stderr = open('E:\\Sublime\\err.txt', 'w')

    n = int(sys.stdin.readline().strip())
    res = 0
    # a, b = map(int, sys.stdin.readline().strip().split()[:2])
    k = int(math.log10(n))
    # print(k)
    for i in range(k):
        res += pow(2, i)

    for i in range(10 ** k, n + 1):
        check = True
        s = str(i)
        for k in s:
            if k != '0' and k != '1':
                check = False
        if check:
            res += 1
    print(res)

if __name__ == '__main__':
    main()

# hajj
#  　　　　　　 ＿＿
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# 　／￣|　　 |　|　|
# 　| (￣ヽ＿_ヽ_)__)
# 　＼二つ
