int const relay1=13, relay2=12;
int const pb1=2, pb2=3, pb3=4, pb4=5;
int pb1stat,pb2stat,pb3stat,pb4stat;

void setup()
{ pinMode(relay1, OUTPUT);
  pinMode(relay2, OUTPUT);
  pinMode(pb1, INPUT_PULLUP);
  pinMode(pb2, INPUT_PULLUP);
  pinMode(pb3, INPUT_PULLUP);
  pinMode(pb4, INPUT_PULLUP);
  digitalWrite(relay2,HIGH);
}

void loop()
{ pb1stat = digitalRead(pb1);
  pb2stat = digitalRead(pb2);
  pb3stat = digitalRead(pb3);
  pb4stat = digitalRead(pb4);
  
  if(pb1stat==0 || pb2stat==0)
  {
    digitalWrite(relay1,HIGH);
    digitalWrite(relay2,LOW);
  }

  if(pb3stat==0 || pb4stat==0)
  {
    digitalWrite(relay1,LOW);
    digitalWrite(relay2,HIGH);
  } 
}
//LAB UC 3
// void loop()
// { pb1stat = digitalRead(pb1);
//   pb2stat = digitalRead(pb2);
  
//   if(pb1stat==0 && pb2stat==0)
//     digitalWrite(relay, HIGH);
//   else
//     digitalWrite(relay, LOW);
// }

//LAB UC 2
// void loop()
// { if(digitalRead(pb)==1)
//     digitalWrite(relay, HIGH);
//   else
//     digitalWrite(relay, LOW);
// }

//LAB UC 1
// void loop()
// { if(digitalRead(pb)==0)
//   { digitalWrite(relay, HIGH);
//   }
//   else  
//     digitalWrite(relay, LOW);
// }