#define S1 4
#define S2 5
#define S3 6
#define S4 7
#define P 3
bool R1, R2, R3, R4;
void setup() {
  // put your setup code here, to run once:
pinMode(S1 ,INPUT_PULLUP);
pinMode(S2 ,INPUT_PULLUP);
pinMode(S3 ,INPUT_PULLUP);
pinMode(S4 ,INPUT_PULLUP);
pinMode(P ,OUTPUT);
}

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


R1 = !digitalRead(S1);
R2 = !digitalRead(S2);
R3 = !digitalRead(S3);
R4 = !digitalRead(S4);
if ((R1 && !R2 && !R3 && !R4) || (R1 && R2 && !R3 && !R4) || 
    (R1 && R2 && R3 && !R4) || (R1 && !R2 && R3 && !R4) || 
    (R1 && !R2 && !R3 && R4) || (!R1 && R2 && !R3 && !R4) || 
    (!R1 && R2 && R3 && !R4) || (!R1 && R2 && !R3 && R4) || 
    (!R1 && !R2 && R3 && !R4) || (!R1 && !R2 && !R3 && R4)) 
  digitalWrite(P, HIGH);
 else 
  digitalWrite(P, LOW);
}