# Unable to recognise little-endian format

I'm told that the input register is in little-endian format. But the vscode gives me error telling me that it is wrong argument for QFT even after using a suitable converter. Am I missing something here?

    operation Task31 (qs : Qubit[]) : Unit {
X(qs[Length(qs)-1]);
ApplyReversedOpBE(QFT, qs);
}


## 1 Answer

You'll need to cast your qubit array as type LittleEndian:

let LEArray = LittleEndian(qs);


A good example of this is in the QuantumKatas under Quantum Phase Estimation.