```
class Queue(object):
def __init__(self):
"""
initialize your data structure here.
"""
self.s1 = []
self.s2 = []
def push(self, x):
"""
:type x: int
:rtype: nothing
"""
self.s1.append(x)
def pop(self):
"""
:rtype: nothing
"""
if len(self.s2)==0:
while self.s1:
self.s2.append(self.s1.pop())
return self.s2.pop()
def peek(self):
"""
:rtype: int
"""
if len(self.s2)==0:
while self.s1:
self.s2.append(self.s1.pop())
return self.s2[-1]
def empty(self):
"""
:rtype: bool
"""
if not self.s1 and not self.s2:
return True
else:
return False
```