void setup() {
  // put your setup code here, to run once:
Serial.begin(9600); 
pinMode(12, OUTPUT);
pinMode(8 ,OUTPUT);
pinMode(15,  INPUT_PULLUP);
pinMode(16,  INPUT_PULLUP);
pinMode(17,  INPUT_PULLUP);
randomSeed(analogRead(0));
boolean rndFlag ;
int a = 0;
int b = 0;
int c = 0;

}

void loop() {
boolean rndFlag = false;
int a =1;
int b = 1;
int c = 1;
a = 1;
b = 1;
c = 1;
a=digitalRead(15);
b=digitalRead(16);
c=digitalRead(17);

if ((a==0)||(b==0)||(c==0))
   { Serial.print(a);
     Serial.print(b);
     Serial.println(c);

    bool rndFlag = !random(3);
    Serial.println(rndFlag);

    if (rndFlag==true) {digitalWrite(8, HIGH);digitalWrite(12,LOW); }
    if (rndFlag==false){digitalWrite(12, HIGH);digitalWrite(8, LOW);}
    delay(3000);
   }

 digitalWrite(12, LOW);
 digitalWrite(8, LOW);  

}