const int L = 3;
const int I = 5;
const int N = 4;
const int K = 6;

void setup() {
  pinMode(L, OUTPUT);
  pinMode(I, OUTPUT);
  pinMode(N, OUTPUT);
  pinMode(K, OUTPUT);
}

void loop() {
  digitalWrite(L, HIGH);
  delay(1000); // in ms
  digitalWrite(L, LOW);
  digitalWrite(I, HIGH);
  delay(1000); // in ms
  digitalWrite(I, LOW);
  digitalWrite(N, HIGH);
  delay(1000); // in ms
  digitalWrite(N, LOW);
  digitalWrite(K, HIGH);
  delay(1000); // in ms
  digitalWrite(K, LOW);
}