int S0 = A0;
int S1 = A1;
int S2 = A2;
int S3 = A3;

void setup() {
  // put your setup code here, to run once:
pinMode(S0,OUTPUT);
pinMode(S1,OUTPUT);
pinMode(S2,OUTPUT);
pinMode(S3,OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

}