void setup() {
  
  pinMode(A2, OUTPUT);
  pinMode(A3, OUTPUT);
  pinMode(A7, INPUT_PULLUP);
}

void loop() {

  if (digitalRead (A7) == LOW) {
  digitalWrite(A2, HIGH); 
  digitalWrite(A3, LOW); 
  delay (500); 
  digitalWrite(A2, LOW); 
  digitalWrite(A3, HIGH); 
  delay (500);
  
  }

  else if (digitalRead (A7)== HIGH){

  digitalWrite (A2, LOW);
  digitalWrite(A3, LOW);
  }
}