const int led_pin_1 = 13;
const int led_pin_2 = 12;
const int led_pin_3 = 11;
const int freq = 2;
const int time = 1000;
const int default_state = LOW;

int blink(const int ledpin, const int state, const int freq, const int time);


void setup() {
  pinMode(led_pin_1, OUTPUT);
  pinMode(led_pin_2, OUTPUT);
  pinMode(led_pin_3, OUTPUT);
}

void loop() {
  blink(led_pin_1, default_state, freq, time);
  blink(led_pin_2, default_state, freq, time);
  blink(led_pin_3, default_state, freq, time);
}
/**
 * Blink the led 'freq' number of times in 'time' milliseconds
 * Invariants:
 * ------------
 * - Pause after every state change
 * - Always end with the initial state
 * - A cycle of blink is two state changes with two delays in between

 * @ledpin: ledpin label
 * @state: initial/default state HIGH or LOW
 * @freq: frequency (> 0)
 * @time: total time of event (> 0 in milliseconds)
 * returns: number of blinks
 */
int blink(const int ledpin, const int state, const int freq, const int time) {
  int x = 0;
  
  for (x; x < freq; x++) {
    digitalWrite(ledpin, !state);
    delay(time / (2 * freq));
    digitalWrite(ledpin, state);
    delay(time / (2 * freq));
  }
  return freq;
}