Elgamal Protocol Failure
Note the relation between $r_1$ and $r_2$
Infer the relationship internal variables need to have because of this
Write down the equations to calculate $(r_1,s_1),(r_2,s_2)$ and use the above relationship
Pretend the equations would be over $\mathbb R$ and solve the above system of equations for $a$
Now plug-in the values and actually perform the modular arithmetic
You now should have recovered the private key