void krug(int x, int y, int radijus) {
  stroke(255);
  strokeWeight(2);
  noFill();
  ellipseMode(RADIUS);
  ellipse(x, y, radijus, radijus);
}

void setup() {
  size(640, 360);
  smooth();
  background(0);
  krug(50, 100, 120);
  krug(width/2, height/2, 50);
  krug(500, 250, 70);
}