Implement a quantum oracle on N qubits which implements a function f(x) = xk, i.e. the value of the function is the value of the k-th qubit.

For an explanation on how the quantum oracles work, see the tutorial blog post.

Input

You have to implement an operation which takes the following inputs:

• an array of qubits x (input register),
• a qubit y (output qubit),
• 0-based index of the qubit from input register K ($$0 \leq K < \text{Length}(x)$$).

The operation doesn't have an output; the "output" of your solution is the state in which it left the qubits.

Your code should have the following signature:

见题面 Input 部分

见题面 Output 部分