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); 
      }
      }