Whose head did the woman of Sheba cast over the wall to Joab?

The head of Sheba

And the woman said unto Joab, Behold, his head shall be thrown to thee over the wall.

Then the woman went unto all the people in her wisdom. And they cut off the head of Sheba the son of Bichri, and cast it out to Joab. 2 Samuel 20:21-22