# Reverse Polish Notation and numbers $>9$

Excuse me for the newbish question in advance but how should I make sure I don't make a mistake converting from RPN to infix notation when I don't know if some of the numbers aren't two-digit ones or when I do that some are but I don't know which ones? For example, how do I know if I should evaluate $112+$ to $11+2$ or $1+12$? Or such thing is impossible to evaluate when I don't know where the enters were put in?

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