int servoPin = A3;
int servoPosition = 0;

Servo myServo;

void setup() {
    
    // attaches the servo on the A3 pin to the servo object
    myServo.attach( A3 );

   //Register our Particle to control the servo
   Particle.function("servo", servoControl);
   
   // Keep a cloud variable for the current position
   Particle.variable( "servoPosition" , &servoPosition , INT );

}

void loop() {

}

int servoControl(String command)
{
    // Convert
   int newPosition = command.toInt();
   
   // Make sure it is in the right range And set the position
   servoPosition = constrain( newPosition, 0 , 180);

   // Set the servo
   myServo.write( servoPosition );

   // done
   return 1;
}