question of using iterator

edit

I want to set the iterator to the specified element of the matrix, but the output is nothing or messy code. The codes are following. pleace help me to understand.Thank you!

#include<iostream>
#include<opencv2/core/core.hpp>
#include<opencv2/highgui/highgui.hpp>

using namespace std;
using namespace cv;
int main()
{

    Point2i pi(0,0);
    Mat n=(Mat_<float>(2,2) << 1.0f, 2.0f, 3.0f, 4.0f);
    Mat* m=& n;
    MatConstIterator ito(m, pi);
    cout <<(*ito);
    system("pause");

}