expected '}' before 'else' Hatası Nasıl Çözülür?

void setup() {

 pinMode(8, OUTPUT);
 pinMode(9, OUTPUT);
 pinMode(10, OUTPUT);
 Serial.begin(9600);

}

void loop() {

  if(Serial.available())
  {
    char a = Serial.read();
    if(a == '1')
    {
      digitalWrite(8, HIGH);
      Serial.println("Led yandi");
    }
    char b = Serial.read();
    else if(b == '1')
    {
      digitalWrite(9, HIGH);
      Serial.println("Led Yandi");
    }
    char c = Serial.read();
    else if(c == '1')
    {
      digitalWrite(10, HIGH);
      Serial.println("Led Yandi");
    }
    char d = Serial.read();
    else if(d == '1')
    {
      digitalWrite(8, LOW);
      digitalWrite(8, LOW);
      digitalWrite(8, LOW);
      Serial.println("Ledler Sondü");    
    }
    else
    {
      digitalWrite(8, LOW);
      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
    }
  }
}