Retrieve Shape text when more than 255 characters inside shape

I have a shape (rectangle) in wich a user writes info. Usually there are more than 255 characters inside that shape. I need to store that text in a variable.

I have tried

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also tried:

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In both cases, my variable "InputText" only stores 255 characters.

How can I get the complete amount of characters in that box when exceeding the 255 characters?

Thanks.