void isr_led2();

void setup() {
  pinMode(PA0, INPUT_PULLDOWN);
  pinMode(PA1, OUTPUT);
  pinMode(PA2, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(PA0), isr_led2, RISING);
}

void isr_led2() {
  digitalWrite(PA2, !digitalRead(PA2));
}

void loop() {
  digitalWrite(PA1, !digitalRead(PA1));
  delay(1000);
}