int led[4] = {PC13,PC14,PC15,PA4};
void setup() {
  for(int i =0;i<4;i++){
    pinMode(led[i],OUTPUT);
  }
  
}

void loop() {
 for(int i =0;i<4;i++){
    digitalWrite(led[i],HIGH);
     delay(1000);
  }
  for(int i =0;i<4;i++){
    digitalWrite(led[i],LOW);
     delay(1000);
  }
}