const int led[4] = {12,11,10,9};
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);
}

void loop() {
 statusPb = digitalRead(pb);
 delay (100);
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;
  }
}