dd: write to multiple disks?

I have 2 exactly same formatted, same size and same brand SD-cards. I would like to dd image to /dev/disk2 and to /dev/disk3 at the same time. Pseudocode sudo dd bs=1m if=/Users/masi/2016-05-10-raspbian-jessie.img of={/dev/disk2,/dev/disk3} --- How can you dd from one input to many output SDs?