int buttonstate = 0;
void setup() {
  pinMode(PA0,INPUT);
  pinMode(PC13,OUTPUT);

}

void loop() {
  buttonstate = digitalRead(PA0);
  if(buttonstate==HIGH){
    digitalWrite(PC13,HIGH);
    delay(1000);
  }
    else {
      digitalWrite(PC13,LOW);
      delay(1000);
    }
  }