Opencv Rect only creating one rectangle

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In my attempt to implement particle filter, I have first manually drawn a rectangle(x,y,w,h) around the car in my image (in red color), then i took 50 particles, and assigned them noise i.e x=x+noise(0,15) and y=y+noise(0,15).

Then i wanted to draw all the rectangles for each particle in green color, but instead of showing 50 rectangles, it is only showing one rectangle.

#include<opencv2\core\core.hpp>
#include<opencv2\imgproc\imgproc.hpp>
#include<opencv2\highgui\highgui.hpp>

#include<stdio.h>
#include<iostream>
#include<random>

using namespace cv;
using namespace std;



const int N = 50;// no of particles

string intToString(int number){

    //this function has a number input and string output
    std::stringstream ss;
    ss << number;
    return ss.str();
}



int main()
{


    Mat frame;
    frame = imread("f (1).png");
    namedWindow("Out");


    //locating the car manually
    Rect car(175, 210, 42, 31);


    //making a rectangle around the car
    rectangle(frame, car, Scalar(0, 0,255), 1, 8, 0);



    //getting tht height and width of the frame
    const int FRAME_HEIGHT = frame.rows;
    const int FRAME_WIDTH = frame.cols;


    //Particle filter initialization

    Mat Init = (Mat_<float>(4, 1) << car.x, car.y, 0, 0);


    //for a gaussian noise distribution
    std::default_random_engine generator;
    std::normal_distribution<double> distribution(0, 15);


    //Initializing the particles
    std::vector<cv::Mat> particle(N, cv::Mat(4, 1, CV_32F));


    cout << car.x << " " << car.y << "\n";

    for (int i = 0; i < N; i++)
    {
        particle[i].at<float>(0, 0) = Init.at<float>(0, 0) + distribution(generator);
        particle[i].at<float>(1, 0) = Init.at<float>(1, 0) + distribution(generator);
        particle[i].at<float>(2, 0) = 0.0;
        particle[i].at<float>(3, 0) = 0.0;
        cout << particle[i] << "\n";
    }

    for (int i = 0; i < N; i++)
    {
        int x = particle[i].at<float>(0, 0);
        int y = particle[i].at<float>(1, 0);

        rectangle(frame, Rect(x, y, 42, 31), Scalar(0, 255, 0), 1, 8, 0);
    }

    imshow("Out", frame);


    waitKey();





    return 0;
}

The output looks like this

The particle x y coordinates are in the following image, The first entry is of the the car that was manually hard coded, rest all are the particle coordinates.