A question can only be stupid if it is stated in a stupid way. Your question gave a clear picture of your situation, and what you wanted to achieve, so - voila! - @Astounding was able to quickly come up with a solution for you. So your question was a good question typical for a beginner, and it was one of those that are a pleasure to answer. Such questions can never be considered "stupid"!
Just one hint for the future: it helps us greatly when example data is provided in a way that makes it easy for us to recreate your datasets quickly and independent from the environment we use. So we like to present data in a data step, which might have looked like that in your case:
data have;
input number_of_obs month1 month2 month3 month4 month5 month6;
cards;
4 50 25 . 10 . .
5 50 25 . . 10 .
;
run;
Just mastering the creation of a dataset with a data step like this provides a learning experience on its own (it was for me).
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