Input file: | Standard input | Time limit: | 1 sec | |

Output file: | Standard output | Memory limit: | 512 Mb |

You are to implement class `Set`

in which the basic operations on sets are implemented:

`Set Union(const Set&) const`

,

`Set Intersection(const Set&) const`

,

`Set Difference(const Set&) const`

,

`Set SymmetricDifference(const Set&) const`

.

It is also necessary to implement a constructor
`Set(const std::vector`

and functions for adding,
removing and checking the presence of an element in the set:

`void Add(int64_t)`

,

`void Remove(int64_t)`

, `bool Contains(int64_t) const`

.

Also, implement the method `std::vector`

that will be
used to access the elements of the set.

The class is supposed to be used to store integers of type `int64_t`

. For storing items
you should use `std::vector`

with the appropriate template parameter

The file with the solution must contain only the implementation
of the described class, without a *main*