const int ButtonPins[4] = { 2, 3, 4, 5};
const int LedPins[4] = { 10, 11, 12, 13};

void setup() 
{
  // Serial.begin(9600);      // Serial output is not used yet.

  // Set the pins for the buttons
  for( int i=0; i<4; i++)
  {
    pinMode( ButtonPins[i], INPUT_PULLUP);
  }

  // Set the pins for the leds
  for( int i=0; i<4; i++)
  {
    pinMode( LedPins[i], OUTPUT);
  }
}


void loop() 
{
  // check if the buttons are pressed and light up the corresponding LED
  for( int i=0; i<4; i++)
  {
    if( digitalRead( ButtonPins[i]) == LOW)
    {
      digitalWrite( LedPins[i], HIGH);
    }
    else
    {
      digitalWrite( LedPins[i], LOW);
    }
  }

  delay( 10);    // slow down the sketch
}