int led_state = LOW;   
int button_state;       
int last_button_state; 

void setup() 
{
   
    pinMode(4, OUTPUT);
    pinMode(14, INPUT_PULLUP);
    button_state = digitalRead(14);
}

void loop() 
{
    last_button_state = button_state;    
    button_state = digitalRead(14); 
    delay(10);
    if (last_button_state == HIGH && button_state == LOW) {
        
        led_state = !led_state;
        
        digitalWrite(4, led_state);
  }
}