**Input**: Two qubits stored in an array which are guaranteed to be either in a superposition of the states $\ket{00}$ and $\ket{11}$ or in a superposition of states $\ket{01}$ and $\ket{10}$.

**Output**: 0 if qubits were in the first superposition, 1 if they were in the second superposition.  
The state of the qubits at the end of the operation should be the same as the starting state.
