s = set([1, 2, 3])

print(s)

s = set([1,2,2,3,3])

print(s)

s.add(4)

print(s)

s.add(4)

print(s)

s.remove(2)

print(s)

ss = ['2','1','3']

ss.sort()
print(ss)

a = 'abc'

b = a.replace('a','A')

print(a)

print(b)
