In 2 Samuel 21, What stopped God's three-year famine?

Hanging seven of Saul's sons and grandsons before the Lord.

Let seven men of his sons be delivered unto us, and we will hang them up unto the LORD. ...

and they hanged them in the hill before the LORD: and they fell all seven together, and were put to death. ...

And after that God was intreated for the land. 2 Samuel 21:6-14