void setup() {

  Serial.begin(9600);
  int A = 0, B = -1, C = -2, D = -3;
  D = C;
  C = B;
  B = A;
  Serial.print("A = ");
  Serial.println(A);
  Serial.print("B = ");
  Serial.println(B);
  Serial.print("C = ");
  Serial.println(C);
  Serial.print("D = ");
  Serial.println(D);
}

void loop() {

}