// Pin definition
int ledPin = 13; // LED connected to digital pin 13

void setup() {
  // Set the LED pin as an OUTPUT
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Turn the LED on
  digitalWrite(ledPin, HIGH);
  delay(1000); // Wait for 1 second

  // Turn the LED off
  digitalWrite(ledPin, LOW);
  delay(1000); // Wait for 20 second
}