int relay=13;
void setup() 
  // put your setup code here, to run once:
  serial.begin (9600);
  pinmode(relay,OUTPUT);
  digitalWrite(relay, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
intz=serial.read();
if(z=='a')
{
digitalWrite(relay,low);
serial.print("relay on");
}
if(z=='b')
}
digitalWrite(realy,high);
serial.print("Relayoff");
 }
}