int led;
void setup() {
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
Serial.begin(9600);
Serial.println("What LED? (3-7)");
}

void loop() {

if(Serial.available()){
        led = Serial.parseInt();
    }

  digitalWrite(led, HIGH);
  delay(500);

  for (int pin = 3; pin < 8; pin++) {
    digitalWrite(pin, LOW);
}
//Serial.println(led);
//delay(500);2
}