const int Pin[]={0,1,2,3,4,5,6,7};
const int pot = A0;
void setup() {

  for (int i = 0; i<8;i++){
    pinMode(Pin[i],OUTPUT);
  }
  pinMode(pot,INPUT);
}

void loop() {
  int pot= analogRead(A0);
  pot = map(pot,0,1023,0,7);

  for (int i = 0; i<8;i++){
    digitalWrite(Pin[i],i==pot ? HIGH:LOW);
  }

}