const int led0 = 13;
const int led1 = 12;
const int led2 = 11;
const int led3 = 10;

// declare other required variables

void setup() {
 // Initialize the Led pins as output
 pinMode(led0, OUTPUT);
 pinMode(led1, OUTPUT);
 pinMode(led2, OUTPUT);
 pinMode(led3, OUTPUT);
}


void loop() {
  // implement the toggling logic
for(int i=0; i < 16; i++){
  digitalWrite(led0, bitRead(i, 0));
  digitalWrite(led1, bitRead(i, 1));
  digitalWrite(led2, bitRead(i, 2));
  digitalWrite(led3, bitRead(i, 3));

  // delay for 1 second(16 second for a full cycle)
  delay(1000);
}
  
}