int time = 50;
void setup() {
  // put your setup code here, to run once:
  #define out 7;
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i=7;i<11;i++){
    light(i);
    delay(time);
  }
  
}
void light(int i){
  digitalWrite(i, HIGH);
  delay(time);
  digitalWrite(i, LOW);
}