Stair Climbing Robot

#include <AFMotor.h>
//initial motors pin
AF_DCMotor motor1(1, MOTOR12_1KHZ);
AF_DCMotor motor2(2, MOTOR12_1KHZ);
AF_DCMotor motor3(3, MOTOR34_1KHZ);
AF_DCMotor motor4(4, MOTOR34_1KHZ);

char command;
void setup()
{
  Serial.begin(9600);  //Set the baud rate to your Bluetooth module.
}
void loop(){
  if(Serial.available() > 0){
    command = Serial.read();
    Stop(); //initialize with motors stopped
    //Change pin mode only if new command is different from previous.
    //Serial.println(command);
    switch(command){
    case 'F':
      forward();
      break;
    case 'B':
       back();
      break;
    case 'L':
      left();
      break;
    case 'R':
      right();
      break;
 }
  }
  void forward()
{
  motor1.setSpeed(255); 
  motor1.run(FORWARD); 
  motor2.setSpeed(255); 
  motor2.run(FORWARD); 
  motor3.setSpeed(255);
  motor3.run(FORWARD);
  motor4.setSpeed(255);
  motor4.run(FORWARD);
}
void back()
{
  motor1.setSpeed(255); 
  motor1.run(BACKWARD); 
  motor2.setSpeed(255); 
  motor2.run(BACKWARD); 
  motor3.setSpeed(255); 
  motor3.run(BACKWARD); 
  motor4.setSpeed(255); 
  motor4.run(BACKWARD); 
}
void right()
{
  motor1.setSpeed(255); 
  motor1.run(BACKWARD); 
  motor2.setSpeed(255); 
  motor2.run(BACKWARD); 
  motor3.setSpeed(255); 
  motor3.run(FORWARD);  
  motor4.setSpeed(255); 
  motor4.run(FORWARD);  
}
void left()
{
  motor1.setSpeed(255); 
  motor1.run(FORWARD); 
  motor2.setSpeed(255); 
  motor2.run(FORWARD); 
  motor3.setSpeed(255); 
  motor3.run(BACKWARD); 
  motor4.setSpeed(255); 
  motor4.run(BACKWARD); 
}
void Stop()
{
  motor1.setSpeed(0); 
  motor1.run(RELEASE); 
  motor2.setSpeed(0); 
  motor2.run(RELEASE); 
  motor3.setSpeed(0); 
  motor3.run(RELEASE);
  motor4.setSpeed(0); 
  motor4.run(RELEASE); 
}