int read1;
int read2;
int read3;

int read;

int* readArray[3] = {&read1, &read2, &read3};

int readFunct(){
  for (int i = 0; i < 3; i++){
    if (*readArray[i] == 1){      
      return i + 1;      
    }
  }
  return 0;
}

void setup()
{
  pinMode(10, INPUT_PULLUP);
  pinMode(11, INPUT_PULLUP);
  pinMode(12, INPUT_PULLUP);
  
  Serial.begin(9600);
}

void loop()
{
  read1 = digitalRead(10);
  read2 = digitalRead(11);
  read3 = digitalRead(12);
  
  read = readFunct();

  Serial.print("First Switch ON is n° ");
  Serial.println(read);
  delay(1000);
}