How to Revert to Stock ROM for HTC Desire 816?

Hi guys!
I recently installed a nightly custom ROM(CM 12) from CyanogenMod for my device(HTC desire 816).
Now I wish to revert back to stock ROM from htc.
Please tell me the steps to do it because I cannot flash the stock ROM using the CyanogenMod recovery(Error: Signature Verification Failed) and I cannot find any other custom recovery for my device.
Please help me out ASAP!!