const byte ledPin = 13;
const byte Ledpin2 = 3;
const byte interruptPin = 2;
volatile byte state = LOW;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(Ledpin2, OUTPUT);
  pinMode(interruptPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(interruptPin), blink, CHANGE);
}

void loop() {
  digitalWrite(Ledpin2, HIGH);
  delay(500);
  digitalWrite(Ledpin2, LOW);
  delay(500);
}

void blink() {
  state = !state;
  digitalWrite(ledPin, state);
}