int led=13;
int SW=2;
void setup() {
  // put your setup code here, to run once:
pinMode(led,OUTPUT);
pinMode(SW,INPUT);

}

void loop() {
  int a=digitalRead(SW);
  if (a==LOW)
  {
    digitalWrite(led, HIGH);
    delay(300);
    digitalWrite(led, LOW);
    delay(300);
  }
  else
  {
    digitalWrite(led, LOW);
  }
}