cf 535B Tavas and SaDDas

B. Tavas and SaDDas
time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Once again Tavas started eating coffee mix without water! Keione told him that it smells awful, but he didn’t stop doing that. That’s why Keione told his smart friend, SaDDas to punish him! SaDDas took Tavas’ headphones and told him: “If you solve the following problem, I’ll return it to you.”

The problem is:

You are given a lucky number nLucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

If we sort all lucky numbers in increasing order, what’s the 1-based index of n?

Tavas is not as smart as SaDDas, so he asked you to do him a favor and solve this problem so he can have his headphones back.

Input

The first and only line of input contains a lucky number n (1 ≤ n ≤ 109).

Output

Print the index of n among all lucky numbers.

Sample test(s)
input

output

input

output

input

output

 

 

题意是只由数字4和数字7组成的数称为lucky number。。。给出一个lucky number 问是第几个….

看数据,,10^9.。。打表打法好啊! 大概10S吧。。。出结果…

 

 

 

作者: CrazyKK

ex-ACMer@hust,researcher@sensetime

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