Task: Question Answering
Input (English): Context : Works No. 174 started a modernization programme for the ZSU-57-2 in parallel with the beginning of its serial production in 1957, but this programme was rejected due to the development of new radar-guided SPAAGs armed with small-bore autocannons and another tracked chassis. 
Question : What was the year ZSU-57-2 entered service?
Output (English): 1957