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); 
 }
}