Infix to reverse polish notation (RPN)

I have an example: m = n = p = (-1) ^ (m + n + p) * (m + n + p);
I don’t know what to do with multiple "=". Should I treat them as a sign with the lowest priority or just put them in end of the answer?
That’s what I get when I treat them as sign with the lowest prioryty:
Could you check my answer?