int led=13;
int sw=2;
void setup(){
  //put your setup code here,to run once:
  pinMode(led, OUTPUT);
  pinMode(sw,INPUT_PULLUP);
}
void loop(){
  int a=digitalRead(sw);
  if(a==LOW)
  {
    digitalWrite(led, HIGH);
delay(300);
digitalWrite(led, LOW);
delay(300);
  }
  else
  {
    digitalWrite(led, LOW);
  }
}