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

**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.*
