# El-Gamal like encryption, how can i guess the key?

There is $$p$$ (large prime number), $$g$$ (generator of $$p$$), and $$x_a$$, $$x_b$$, $$r$$ (which are between $$1$$ and $$p-1$$).

I know $$g^{x_a}$$, $$g^{x_b}$$, $$g^r$$, $$g^{x_a\cdot x_b\cdot r} \bmod p$$.

How can I get $$g^{x_a\cdot r}$$?