const int buttonpin=4;
const int ledpin=12;
int buttonstate;
void setup() {
  // put your setup code here, to run once:
  pinMode(ledpin, OUTPUT);
  pinMode(buttonpin, INPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  buttonstate=digitalRead(buttonpin);
  if(buttonstate==LOW){
    digitalWrite(ledpin, HIGH);
    delay(500);
    digitalWrite(ledpin, LOW);
    delay(500);
  }
  else{
    digitalWrite(ledpin, LOW);
  }

}