void setup(){
for(int x=4; x<=13; x++){
pinMode(x, OUTPUT);
}
}
void loop(){
for(int x=4; x<=13; x++){
digitalWrite(x,HIGH);
delay(300);
digitalWrite(x,LOW);
}
for(int x=13; x>=4; x--){
digitalWrite(x,HIGH);
delay(300);
digitalWrite(x,LOW);
}
}