circle

#include<windows.h>
#include <GL/glut.h>
#include <GL/gl.h>
#include <bits/stdc++.h>

using namespace std;

double x1,y11,x2,y2,delx,dely,delm,x,y,pk;

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,0.0,0.0);

    glBegin(GL_POINTS);
        glVertex2i(0,y);
        glVertex2i(y,0);
        glVertex2i(0,-y);
        glVertex2i(-y,0);
        glVertex2i((y/2.00),(y/2.00));
        glVertex2i((y/2.00),-(y/2.00));
        glVertex2i(-(y/2.00),(y/2.00));
        glVertex2i(-(y/2.00),-(y/2.00));
    glEnd();

    glFlush();

}

void init(void)
{
    glClearColor(1,1,1,5.0);
    glMatrixMode(GL_PROJECTION);
    // glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
    glPointSize(39.0);
    glOrtho(-100.0, 100.0, -100.0, 100.0, -100.0, 100.0);

}
int main(int a,char **ar)
{
    glutInit(&a,ar);
    glutInitDisplayMode(GLUT_RED | GLUT_SINGLE);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(800,500);
    glutCreateWindow("Polygon");
    cin >> y ;

    init();
    glutDisplayFunc(display);
    glutMainLoop();

    return 0;

}