please help me!how to check empty ?

[tc101]

i want check the input area is empty or not,
if is empty ,then input some character ，if not then do nothing.
how to determine if empty or not?
thanks you help ,sorry for my bad english!

 

[shinigami]

1. Get value of input (via branch builder)
2. Set branch logic operation. And check if '{executed result of 1}'!=''
3. If yes - set value for input