Problem
Nani from the first minutes disliked Stitch and was even afraid to stay with him in the same house. But after a while, she saw a kind soul in the baby and accepted him into her family. Together with Stitch, his creator Jumbo, who had to stay on Earth, had to be sheltered.
To remember the names of new aliens he knows, Jumbo enters them into the computer. Alien names can contain a wide variety of characters, but always satisfy specific rules. The rules are as follows: all names contain only Latin letters (uppercase and lowercase), numbers and underscores. The name always starts with either a letter or an underscore. There are no other characters in the names.
Write a program for Jumbo that would check if he entered the name of the next acquaintance into the computer correctly.
Input
The input of the program is a character string - the name that Jumbo entered into the computer.
Imprint
The program should output the answer '
YES' if the string is a problem-formed name, and '
NO' otherwise.
Examples
| # |
Input |
Output |
| 1 |
Abc123
|
YES
|
| 2 |
Abc[a!
|
NO
|