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
# RawCoder : https://bit.ly/RCyouTube
# Author : MehulYK

n = int(input())
i = 1
ans = 0
while(i <= n):
    ch = list(set(str(i)))
    if(len(ch) == 1):
        if(ch [0] == '0' or ch[0] == '1'):    
            ans += 1
    elif(len(ch) == 2):
        if(ch [0] == '0' and ch[1] == '1'):    
            ans += 1      
        elif(ch [0] == '1' and ch[1] == '0'):    
            ans += 1
    #st = str(i)
    
    if(str(i).endswith('0')):
        i += 1
        #print(i)
    else:
        i += 9
        #print(i)
    st = str(i)
    if(st[0] != '1'):
        i = '1' + '0'*len(st)
    i = int(i)        
print(ans)                    
