Auto comment: topic has been updated by vivek_ghosh (previous revision, new revision, compare).

You erase a set iterator, that you still later use in a loop.

To prevent that, if you want to erase an element in a set, first increment the iterator pointing to that element, and then erase the iterator previous to it.

Also, when erasing an element, don't dereference the iterator.

Just replace the loop with something like that:

while( it != f.end() )
    if( x % (*it) and y % (*it) )
    { 
        auto iu = it; 

        iu++, f.erase(it), it = iu; 
    }
    else
        it++;

This should fix the problem. Either f.erase(it) or f.erase(*it) can be used to erase the item.

Thanks.