const int GPIO_Pin[]={1,5,9,13};
void setup() {
  // put your setup code here, to run once:
  for(int i=0;i<4;i++)
  {
    pinMode(GPIO_Pin[i],OUTPUT);
    
  }
}
void loop() {
  // put your main code here, to run repeatedly:
 for(int i=0;i<4;i++)
 {
  digitalWrite(GPIO_Pin[i], HIGH);
  delay(1000);
  digitalWrite(GPIO_Pin[i], LOW);
 }
  for(int i=3;i>=0;i--)
 {
  digitalWrite(GPIO_Pin[i], HIGH);
  delay(1000);
  digitalWrite(GPIO_Pin[i], LOW);
 }
}