class Puk:
	def __init__(self):
		self.val = 0
		
	def foo(self, num, reset=False):
		if reset:
			self.val = 0
		self.val += num
		return self.val

a = Puk()
b = Puk()

print(a.foo(10))
print(b.foo(15))
print(a.foo(4))
print(b.foo(3))
print(a.foo(1, reset=True))