Task: Question Understanding
Input (English): Passage: All these problems came to a head on 1 June 1648, upon Alexei I's return to Moscow from the Troitse-Sergiyeva Lavra monastery. A crowd of Muscovites surrounded the Tsar and complained about the boyars and prikaz officials. Instead of hearing the petition, the royal bodyguards started dispersing the crowd, pushing them away from the Tsar. This unexpected reaction caused a major outbreak of anger among the people. On 2 June the insurgents burst into the Moscow Kremlin and demanded the surrender of Leontii Pleshcheyev , Duma diak Nazar Chistoy , boyar Boris Morozov  and his brother-in-law Pyotr Trakhaniotov . Morozov commanded the Streltsy  to drive the rioters out of the Kremlin, but they refused. When not acting as the Tsar's bodyguards, the musketeers held artisanal jobs in Moscow. This conflict of interest led them to side with the plight of the townsmen, stating that they, "...did not want to stand in antagonistic relations with the crowd for the sake of the traitor and tyrant Pleshcheyev." The people would not hear the Tsar's heartfelt pleas to spare Pleshceyev and, on June 3, Alexei surrendered the official. In their fervor, the crowd did not wait for Pleshcheyev to be executed instead, "...they cuggeled him so black and blue and with axes they cut him asunder like a fish, the pieces they let lie naked here and there." The rebels set fire to the White City and Kitai-gorod. They burned between 15,000 and 24,000 houses; between 1700 and 2000 people died in the riot. The rioters split into two groups to target the most hated boyars, diaks, okolnichys, and merchants, killing Nazar Chistoy as he begged for mercy. When rumors spread that Morozov's men had started the fires to antagonize the rioters, the boyar head hunt gained greater momentum.
Question: How many cities did the rebels set fire to?
Output (English): number