const int LED1_pin = 4;
const int LED2_pin = 5;
const int LED3_pin = 6;

unsigned long LED1_time = 0;
unsigned long LED2_time = 0;
unsigned long LED3_time = 0;

int LED1_state = LOW;
int LED2_state = LOW;
int LED3_state = LOW;

const int LED1_on_time = 2000;
const int LED1_off_time = 7000;

const int LED2_on_time = 2500;
const int LED2_off_time = 5000;

const int LED3_on_time = 3000;
const int LED3_off_time = 7000;

void setup() {
  pinMode(LED1_pin, OUTPUT);
  pinMode(LED2_pin, OUTPUT);
  pinMode(LED3_pin, OUTPUT);
}

void loop() {
  unsigned long current_time = millis();
  
  if (current_time - LED1_time >= LED1_on_time && LED1_state == LOW) {
    LED1_time = current_time;
    LED1_state = HIGH;
    digitalWrite(LED1_pin, LED1_state);
  }
  else if (current_time - LED1_time >= LED1_off_time && LED1_state == HIGH) {
    LED1_time = current_time;
    LED1_state = LOW;
    digitalWrite(LED1_pin, LED1_state);
  }
  
  if (current_time - LED2_time >= LED2_on_time && LED2_state == LOW) {
    LED2_time = current_time;
    LED2_state = HIGH;
    digitalWrite(LED2_pin, LED2_state);
  }
  else if (current_time - LED2_time >= LED2_off_time && LED2_state == HIGH) {
    LED2_time = current_time;
    LED2_state = LOW;
    digitalWrite(LED2_pin, LED2_state);
  }
  
  if (current_time - LED3_time >= LED3_on_time && LED3_state == LOW) {
    LED3_time = current_time;
    LED3_state = HIGH;
    digitalWrite(LED3_pin, LED3_state);
  }
  else if (current_time - LED3_time >= LED3_off_time && LED3_state == HIGH) {
    LED3_time = current_time;
    LED3_state = LOW;
    digitalWrite(LED3_pin, LED3_state);
  }
}