const byte LED_1 = 2;
const int LED_2 = 4;
const byte interrupt=3;
volatile byte state_1=LOW;
volatile byte state_2=HIGH;


void setup() {
  // Set the pins as outputs
  pinMode(LED_1, OUTPUT);
  pinMode(LED_2, OUTPUT);
  pinMode(interrupt, INPUT_PULLUP);
cli();
attachInterrupt(digitalPinToInterrupt(interrupt),blink,CHANGE);
sei();

}

void loop() {
  // Run the LEDs
  if(state_1==0){
    digitalWrite(LED_2,state_2);
    delay(1000);
    digitalWrite(LED_2,state_1);
    delay(1000);
    
  }

}
void blink(){
  state_1=!state_1;
  digitalWrite(LED_1,state_1);

}