class Set:
    def __init__(self, value = []):    # constructor
        self.data = []                 # manages a list
        self.concat(value)

    def intersect(self, other):        # other is a sequence
        res = []                       # self is the subject
        for x in self.data:
            if x in other:
                res.append(x)
        return Set(res)                # return a new Set

    def union(self, other):
        res = self.data[:]             # copy of my list
        for x in other:
            if not x in res:
                res.append(x)
        return Set(res)

    def concat(self, value):           # value: list, Set...
        for x in value:                # removes duplicates
           if not x in self.data:
                self.data.append(x)

    def __len__(self):          return len(self.data)
    def __getitem__(self, key): return self.data[key]
    def __and__(self, other):   return self.intersect(other)
    def __or__(self, other):    return self.union(other)
    def __repr__(self):         return 'Set:' + `self.data`