# l=[0 for i in range(2)]
# print(l)
# l=['a','b']
# s=[]
# s.append(l)
# l=['c','d']
# s.append(l)
# for i in s:
#     for j in i:
#         print(j)
# print(s,l)
s=[['a', 0], [0, 'b'], ['c', 0], [0, 'd'], ['e', 0], [0, 'f']]
print(len(s))
print()