Task: Question Answering
Input (English): Passage: The Kiev uprising of 1068 was a revolt against Grand Prince Iziaslav Yaroslavich of Kiev in the aftermath of a Kievan Rus' defeat at the hands of the Cumans at Battle of the Alta River near the city of Pereiaslavl, southeast of Kiev. The Polovtsy raid of 1068-1069 was only the tribe's second major raid into Rus'  in 1055, but the tribesmen broke the treaty and attacked Kievan Rus' six years later, defeating Vsevolod in battle).  In 1068-1069, the Polovtsy penetrated the earthwork defensive lines built up over the years by Prince Vladimir Svyatoslavich  and his son, Yaroslav the Wise .  They were met by a combined army of Yaroslav's sons: Grand Prince Iziaslav of Kiev and his brothers, Princes Sviatoslav Yaroslavich of Chernigov, and Vsevolod, which was defeated and fled back to Kiev in disarray. The Polovsty continued to raid throughout the area, prompting the Kievans to call on the grand prince to rearm them so they could march out and meet the threat.  Iziaslav refused, prompting the rebellion.  The Tale of Bygone Years , a part of The Lavrentian Chronicle, relates what happened next:. 
Question: How many sons did Yaroslav the Wise have? 
Answer type: Number 
Output (English): 3.