int pin_led = 9;
int pin_etat = 8;
int pin_bouton = 7;

void setup()
{
  pinMode(pin_led, OUTPUT);
  pinMode(pin_etat, INPUT);
  pinMode(pin_bouton, INPUT);
}

void loop()
{
  if(digitalRead(pin_bouton) == LOW){
    if(digitalRead(pin_etat) == LOW){
      digitalWrite(pin_led, HIGH);
    }
    else{
      digitalWrite(pin_led, LOW);
    }
  }
}