<s> class Queue : <EOL> def __init__ ( self ) : <EOL> self . A , self . B = [ ] , [ ] <EOL> def push ( self , x ) : <EOL> self . A . append ( x ) <EOL> def pop ( self ) : <EOL> self . peek ( ) <EOL> self . B . pop ( ) <EOL> def peek ( self ) : <EOL> if not self . B : <EOL> while self . A : <EOL> self . B . append ( self . A . pop ( ) ) <EOL> return self . B [ - <NUM_LIT:1> ] <EOL> def empty ( self ) : <EOL> return not self . A and not self . B </s>
