Task: Question Answering
Input (English): Passage: Immediately after cessation of fighting, a summary trial was convened for 36 rebels.  The court convicted 17 for two main offenses:  the murder of 4 German officials and 5 island boatmen, and  for insurrection, and condemned them to death; 12 received multi-year sentences at hard labor, 7 were acquitted and set free. On 24 February 1911, 15 rebels, including Samuel, were executed by a Melanesian police firing squad, 2 of the condemned men through fortunate circumstances managed to avoid the death penalty. The colonial government decided to rid Pohnpei of the troublesome Sokehs and banished the tribe of 426 souls to Babelthuap in the German Palau Islands. 
Question: How many rebels were not put to death? 
Answer type: Number 
Output (English): 21.