Fourteenth.
The fourteenth amendment granted citizenship to all slaves + African Americans.
Fourteenth
The Thirteenth Amendment ended slavery. The next step was to make former slaves citizens. I know this isn't a math class, but I'm betting you know what comes after 13. That's right! It was the Fourteenth Amendment that extended the rights of citizenship to former slaves and anyone else born or naturalized in the U.S.
(Sorry I'm Late!)