A file name consists of \(2\) parts: base name and extension name, separated by a dot character. For example, Python
source code files have extension name "py", documents have extension name "doc" or "docx". In Windows OS, file
names are case insensitive.

Write a program to input a file name as string and check whether it is considered Python source code file in
Windows or not.

Input

• Only one line contain file name \(S (1 < |S| < 128)\). File name will only contain ’a’-’z’,’A’-’Z’,’’ and’_’.

Output

• If file is a python file, print "yes", otherwise "no".

Example

abc.py

yes

abc.bin

no