How to deal with NaN values in prediction using LSTM or RNN, when I can't delete them and can't fill them with median nor mean values?

Hello,
So basically I have realised that I have quite a big problem.
Bascially I am trying out an ideas for stock prediction, and in one case I have calculated ichimoku indicator, which contains a couple of indicators.
One of them is so called chikou-span which bassically is the receded price value by 26 time intervals.

Basically
chikou\_span\[i\] = price\_array\[i - 26\]


For example:
if the price was:
0, 1, 2, 3, 4, 5, ... 25, 26, 27, 28
chikou-span …

deal lstm mean nan neuralnetworks prediction rnn values