#define S1 0
#define S2 1
#define S3 2
#define S4 3

bool S1x,S2x,S3x,S4x;

void setup() {
pinMode(S1, INPUT_PULLUP);
pinMode(S2, INPUT_PULLUP);
pinMode(S3, INPUT_PULLUP);
pinMode(S4, INPUT_PULLUP);
pinMode(, OUTPUT);
}

void loop() {
S1x = !digitalRead(S1);
S2x = !digitalRead(S2);
S3x = !digitalRead(S3);
S4x = !digitalRead(S4);


}