Getting a C2664 Error while trying to build a unique_ptr vector

I'm having issues trying to build a program using a Unique_ptr vector to hold data from multiple classes that are derived from the same base class. I'm pretty sure the concept is correct, so I can avoid slicing my data, but I'm not sure what exactly I'm doing wrong here. Also I'm not sure how I'm supposed to pass a unique_ptr to a function to read it or write it. Any assistance would be greatly appreciated. (Edit, made the code actually comprehensible, sorry for that!)

#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
#include <memory>
using namespace std;


class Base
{
public:
    Base();
    Base(int x, int y, string z) :Z(z), Y(y), X(x){}
    virtual void printstuff(){cout << X << Y << Z; system("pause"); }
    virtual ~Base(){}
protected:
    int X, Y;
    string Z;
};

class Derrived : public Base
{
public:
    Derrived();
    Derrived(int x, int y, string z, int a, int c) : Base(x, y, z), changeable(c), A(a){}
    virtual void printstuff(){cout << X << Y << Z << changeable << A;}
    int changeable;
    ~Derrived(){}
private:
    int A;
};

void otherfunction(vector<unique_ptr<Base>>&);

void main()
{
    vector<unique_ptr<Base>> array1;
    array1.emplace_back(new Derrived (1, 2, "check", 3, 5));
    otherfunction(array1);
    array1[0]->printstuff();

}



void otherfunction(vector<unique_ptr<Base>>& var1)
{
    dynamic_cast<Derrived &>(*var1[0]).changeable = 3;
}

I want the output statement to be 3 for changeable, I'm getting an error C2664 for some reason so I'm not sure what exactly I'm doing wrong, as it doesn't reference a specfic line in my code (the line it references is line 600 of xmemory.h). A copy of the actual code can be found here: Link to the actual code.