int B = 9; 
int L = 8; 
int ledState = LOW; 
int lastButtonState = LOW;
int buttonState;

void setup() {
  pinMode(L, OUTPUT); 
  pinMode(B, INPUT);
  Serial.begin(9600);
  l123 = 0;
}

void loop() {
  buttonState = digitalRead(B); 

  if (buttonState == HIGH && lastButtonState == LOW) { 

    ledState = !ledState;
    digitalWrite(L, ledState);
  }

  lastButtonState = buttonState; 
  delay(50);
}