int L1 = 1;
int L2 = 2;
int L3 = 3;
int L4 = 4;
int L5 = 5;
int L6 = 6;
int time = 100;

void setup() {
pinMode(L1, OUTPUT);
pinMode(L2, OUTPUT);
pinMode(L3, OUTPUT);
pinMode(L4, OUTPUT);
pinMode(L5, OUTPUT);
pinMode(L6, OUTPUT);
}

void loop() {
digitalWrite(L1, HIGH);
delay(time);  digitalWrite(L1, LOW);
delay(time);
digitalWrite(L2, HIGH);
delay(time);
digitalWrite(L2, LOW);
delay(time);
digitalWrite(L3, HIGH);
delay(time);
digitalWrite(L3, LOW);
delay(time);
digitalWrite(L4, HIGH);
delay(time);
digitalWrite(L4, LOW);
delay(time);
digitalWrite(L5, HIGH);
delay(time);
digitalWrite(L5, LOW);
digitalWrite(L6, HIGH);
delay(time);
digitalWrite(L6, LOW);
delay(time);
delay(time);
digitalWrite(L4, HIGH);
delay(time);
digitalWrite(L4, LOW);
delay(time);
digitalWrite(L3, HIGH);
delay(time);
digitalWrite(L3, LOW);
delay(time);
digitalWrite(L2, HIGH);
delay(time);
digitalWrite(L2, LOW);
}