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Sat, 06 Jun 2026 00:00:00 +0000

#022 · Nearly Lucky Number · strings · medium · python


Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal
representations contain only the lucky digits 4 and 7.
For Example numbers: 47, 477, 4 are lucky and 5, 17, 467 are not.
Unfortunately, not all numbers are lucky. Petya calls a number nearly lucky if the number of
lucky digits in it is a lucky number.
Input:
the only line contains an integer n (1 Because Count of lucky number in 400447 is a lucky number also (4)!
### Example Input:

### Example Output:

YES


### Example Input:

1000000000000000000000000000

### Example Output:

NO

Lucky-Digits on Python Exercises

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