const int led[4]={9,10,11,12};
const int pb=(A4);
bool statuspb;
int x=0;

void setup() {
  for (int i=0; i<4; i++){
    pinMode(led [i], OUTPUT);
  }
  pinMode(pb, INPUT);
  // put your setup code here, to run once:

}

void loop() {
  statuspb = digitalRead(pb);
  delay(300);
  if (statuspb ==1){
    x++;
  }
  switch (x){
    case 0:
    digitalWrite(led [0], HIGH);
    digitalWrite(led [1], LOW);
    digitalWrite(led [2], LOW);
    digitalWrite(led [3], LOW);
    break;
    case 1:
    digitalWrite(led [0], LOW);
    digitalWrite(led [1], HIGH);
    digitalWrite(led [2], LOW);
    digitalWrite(led [3], LOW);
    break;
    case 2:
    digitalWrite(led [0], LOW);
    digitalWrite(led [1], LOW);
    digitalWrite(led [2], HIGH);
    digitalWrite(led [3], LOW);
    break;
    case 3:
    digitalWrite(led [0], LOW);
    digitalWrite(led [1], LOW);
    digitalWrite(led [2], LOW);
    digitalWrite(led [3], HIGH);
    break;
    default:
    if (x>=4){
      x=0;
    }
    break;

  }
}