It's the one on the left. We're allowed any calculator that's not programmable and cannot store text. The Elektronika can be programmed though it cannot store a program when turned off.
Nevermind the Casio's ability to solve, integrate, derivate, deal with complex numbers and matrices and more
The rule is completely understandable, I don't think there are many programmable calculators with no storage. I still find it funny though.