const int green = 27,red=19;
void setup() {
  Serial.begin(115200);
  pinMode (green, OUTPUT);
  pinMode (red, OUTPUT);
}
void loop() {
  digitalWrite (green, HIGH);	
  digitalWrite (red, LOW);
  delay(1000);	
  digitalWrite (red, HIGH);	
  digitalWrite (green, LOW);
  delay(1000);	
}