What these alphabets stands for?

Sorry if this question is trivial but I couldn’t find the answer in the internet,

In pytorch documentation I saw these large alphabets in formulas
like:
Input:(N, C, H^in, W^out)
link: https://pytorch.org/docs/stable/generated/torch.nn.MaxPool2d.html

So what are these stands for and where
I can find the meaning of these alphabets.

>Solution :

Those are typical axis notations used in the PyTorch documentation to refer to the dimension sizes:

• N: batch size
• C: number of channels
• W: the width of the tensor
• H: the height of the tensor

Suffix _in and _out stand for the axis’ corresponding input and output size respectively.