#define buttonAPin 13
#define buttonBPin 15
#define led 21

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(buttonAPin, INPUT_PULLUP);
  pinMode(buttonBPin, INPUT_PULLUP);
  pinMode(led, OUTPUT);
}

int status = 0;
void loop() {
  // put your main code here, to run repeatedly:
  if (!digitalRead(buttonAPin)) {
    status = 1;
  } else if (!digitalRead(buttonBPin)) {
    status = 0;
  }
  digitalWrite(led, status);
}