int main(int argc, char** argv){
  glutInit(&argc,argv);
  glutInitWindowPosition(50,50);
  glutInitWindowSize(640,640);
  glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
  glutCreateWindow("Circle");
  glMatrixMode(GL_PROJECTION);
  gluOrtho2D(0,100,0,100);
  glutDisplayFunc(display);
  glutMainLoop();
  return 0;
}