Task: Question Answering
Input (English): Passage: The repressions by the Bolshevik government of Armenia created widespread discontent and the Armenian Revolutionary Federation began a rebellion on February 13. By February 17 Ashtarak, Ejmiatsin, Garni, and Hrazdan were taken over by ARF forces. On February 18 they entered Yerevan. The Bolsheviks and the Red Army retreated to Artashat. Hovhannes Katchaznouni, Levon Shant, Nikol Aghbalian and 100 other political activists and intellectuals were freed from jails. After the capture of Yerevan, the Salvation Committee of the Fatherland was founded under the leadership of former Prime Minister Simon Vratsian, which was to govern the country until the formation of a new government. The committee addressed the population on February 18 which invoked people to "protect order and rule, strictly fulfill all the orders of the committee". Throughout the 42-day rebellion, bloody battles took places between ARF forces and the Bolsheviks. On February 27 the Bolsheviks tried to attack Yerevan but on March 1 they were forced to retreat. After a two-week pause, Bolshevik units again attacked and took over Artashat on March 16 but the next day ARF forces started an offensive and recaptured the town. The Bolshevik forces, greatly outnumbering the ARF, began a large offensive on March 24. They captured Aparan, Kotayk and gradually emerging, entered Yerevan on April 2. The ARF forces retreated without any serious battle to avoid the destruction of the capital. 
Question: How many days after beginning the rebellion, were the Bolsheviks forced to retreat from Yerevan ? 
Answer type: Number 
Output (English): 16.