const int LED1 = 11;  // LED1 connected to digital pin 13
const int LED2 = 10;  // LED2 connected to digital pin 12
const int LED3 = 9;  // LED3 connected to digital pin 11
const int button1 = 2;  // button1 connected to digital pin 2
const int button2 = 3;  // button2 connected to digital pin 3
const int button3 = 4;  // button3 connected to digital pin 4

void setup()
{
  pinMode(LED1, OUTPUT);  // sets the LED1 as an output
  pinMode(LED2, OUTPUT);  // sets the LED2 as an output
  pinMode(LED3, OUTPUT);  // sets the LED3 as an output
  pinMode(button1, INPUT_PULLUP);  // sets the button1 as an input with pull-up resistor
  pinMode(button2, INPUT_PULLUP);  // sets the button2 as an input with pull-up resistor
  pinMode(button3, INPUT_PULLUP);  // sets the button3 as an input with pull-up resistor
}

void loop() {
  // reads the button1 state and turns on/off LED1 accordingly
  if (digitalRead(button1) == LOW) {
    digitalWrite(LED1, HIGH);
  } else {
    digitalWrite(LED1, LOW);
  }

  // reads the button2 state and turns on/off LED2 accordingly
  if (digitalRead(button2) == LOW) {
    digitalWrite(LED2, HIGH);
  } else {
    digitalWrite(LED2, LOW);
  }

  // reads the button3 state and turns on/off LED3 accordingly
  if (digitalRead(button3) == LOW) {
    digitalWrite(LED3, HIGH);
  } else {
    digitalWrite(LED3, LOW);
  }
}