int ledpin=3;
int buttonpin=12;
int buttonread;
int dt=500;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(ledpin,OUTPUT);
pinMode(buttonpin, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
buttonread=digitalRead(buttonpin);
Serial.println(buttonpin);
delay(dt);

while (buttonread==1) {
digitalWrite(ledpin, HIGH);
buttonread=digitalRead(buttonpin);
Serial.println(buttonpin);
delay(dt);

}
digitalWrite(ledpin, LOW);
}