C++: create vector 3 while looping thought 2 others

I'm totally newbie in C++ and I need to solve a problem with vectors. What I need is to merge two existing vectors and create third one. While I saw several answers, the difference here is I need vector #3 (values3) to contain not all values, but only those which are in both vectors #1 (values1) and #2 (values2). So, if integer 2 is in vector 1 but is not in vector 2, this number does not fit me. I should use a function provided below. Commented lines are which I don't know what to write in. Other lines are working.

void CommonValues(vector<MainClass> & values1, vector<MainClass> & values2, vector<MainClass> & values3)
{
    MainClass Class;
    string pav;
    int kiek;
    vector<MainClass>::iterator iter3; // ?
    for (vector<MainClass>::iterator iter1 = values1.begin(); iter1 != values1.end(); iter1++)
    {
        for (vector<MainClass>::iterator iter2 = values2.begin(); iter2 != values2.end(); iter2++)
        {
            if (iter1 == iter2)
            {
                pav = iter2->TakePav();
                iter3->TakePav(pav); // ?
                kiek = iter1->TakeKiek() + iter2->TakeKiek();
                iter3->TakeKie(kiek); // ?
                iter3++; // ?
            }
        }
    }
}