int[] numbers = new int[4];

void setup() {
  size(400, 400);
  
  numbers[0] = 100;
  numbers[1] = 300;
  numbers[2] = 60;
  numbers[3] = numbers[2] * 3;
}

void draw() {
  background(0);
  for (int i = 0; i < 4; i++) {
    rect(numbers[i], mouseY, 20, 20);
  }
}