int sigma = 12;
int alpha = 14;

void setup() {
  pinMode(sigma,OUTPUT);
  pinMode(alpha, OUTPUT);
  digitalWrite(sigma, HIGH);
  digitalWrite(alpha, HIGH);
}

void loop() {
  digitalWrite(sigma,HIGH);
  delay(500);
  digitalWrite(sigma,LOW);
  digitalWrite(alpha,HIGH);
  delay(500);
  digitalWrite(alpha,LOW);
  delay(500);
}