HOW MANY YEARS OF FAMINE DID THE ANGEL GAD THREATEN DAVID WITH?

II Samuel 24:13 So Gad came to David, and told him, and said unto him, Shall seven years of famine come unto thee in thy land? or wilt thou flee three months before thine enemies, while they pursue thee? or that there be three days' pestilence in thy land? now advise, and see what answer I shall return to him that sent me. (KJV) I Chronicles 21:12 Either three years' famine; or three months to be destroyed before thy foes, while that the sword of thine enemies overtaketh thee; or else three days the sword of the LORD, even the pestilence, in the land, and the angel of the LORD destroying throughout all the coasts of Israel. Now therefore advise thyself what word I shall bring again to him that sent me. (KJV)

These are actually two different situations being described here.  Reading the passages around it, you will see that the 2 Samuel threat happens before David repents, and the 1 Chronicles situation happens after David repents.  Due to David's repentance, God lowered the threat of famine from seven years to three years.  Not a contradiction.