Optional and uninitialized

I want to assign a value for an optional.

#include <iostream>
#include <string>
#include <boost/optional.hpp>
int main()
{
   
    boost::optional<int> x;
    int y;
    x = y;
    if (not x)
    {
        std::cout<<"none";
    }
    else
    {
        std::cout<<"not none";
    }
}

It will be not none though y is uninitialized, how should I proceed to get none for an optional if the right value was not initialized ? Thanks.