new code

// Standard include files

#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/tracking/tracking.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/video.hpp>
#include <opencv2/imgcodecs.hpp>


using namespace cv;
using namespace std;

int main(int argc, char **argv)
{
    // Set up tracker.
    // Instead of MIL, you can also use
    // BOOSTING, KCF, TLD, MEDIANFLOW or GOTURN
    Ptr<Tracker> tracker = Tracker::create( "MIL" );

    VideoCapture cap(0); //capture the video from webcam

       if ( !cap.isOpened() )  // if not success, exit program
       {
            cout << "Cannot open the web cam" << endl;
            return -1;
       }

       Mat frame;
       cap>>frame;
       cap.read(frame);


    // Define an initial bounding box
    Rect2d bbox(287, 23, 86, 320);

    // Uncomment the line below if you
    // want to choose the bounding box
    // bbox = selectROI(frame, false);

    // Initialize tracker with first frame and bounding box
    tracker->init(frame, bbox);

    while(cap.read(frame))
    {
        // Update tracking results
        tracker->update(frame, bbox);

        // Draw bounding box
        rectangle(frame, bbox, Scalar( 255, 0, 0 ), 2, 1 );

        // Display result
        imshow("Tracking", frame);
        int k = waitKey(1);
        if(k == 27) break;

    }

    return 0;

}