# How many ancilla qubits to use with Multiple-Control Toffoli (mct) gate in Qiskit?

The Multiple-Control Toffoli (mct) gate takes as input: 1. a register containing the control qubits, 2. the target qubits and 3. a register containing ancilla qubits.

I don't know how many ancilla qubits I need to pass in for a number of $$n$$ controll qubits. I've seen examples and used mct gates with 4 control qubits and 2 ancillas so I know the number of ancillas is not $$n-1$$ like suggested in this answer

Is there a strict dependency meaning for 10 control qubits you need 5 ancillas or does the implementation adapt to the number or ancillas that are passed in?

I found out the number of ancillas is minimum $$n-2$$.
if len(ancillary_qubits) < len(control_qubits) - 2: