#define motora 0
#define motorb 1
#define motorc 2
#define motord 3

#define controla 0 
#define controlb 1
#define controlc 2 
#define controld 3

#define deadzone 50

void main() 
{

  int a, b, c, d;

  while(1) {

    printf("ESG robotics     (press START)\n");

    while (start_button() == 0) {}

    printf("ESG robotics     (press STOP)\n");

    while (stop_button() == 0) {

      a = analog(controla) - 128;     /* now it's from -128 to 127 */
      b = analog(controlb) - 128;     /* now it's from -128 to 127 */
      c = analog(controlc) - 128;     /* now it's from -128 to 127 */
      d = analog(controld) - 128;     /* now it's from -128 to 127 */


      /* make a zone in the middle of the sensor where the motor's off */

      if ((a <= deadzone) && (a >= -deadzone)) { 
	motor(motora,0); 
      }
      else {
	if (a < 0) { 
	  a = a + 28;
	  motor(motora,a);
	}
	else {
	  a = a - 27;
	  motor(motora,a);
	}
      }
      if ((b <= deadzone) && (b >= -deadzone)) { 
	motor(motorb,0); 
      }
      else {
	if (b < 0) { 
	  b = b + 28;
	  motor(motorb,b);
	}
	else {
	  b = b - 27;
	  motor(motorb,b);
	}
      }
      if ((c <= deadzone) && (c >= -deadzone)) { 
	motor(motorc,0); 
      }
      else {
	if (c < 0) { 
	  c = c + 28;
	  motor(motorc,c);
	}
	else {
	  c = c - 27;
	  motor(motorc,c);
	}
      }
      if ((d <= deadzone) && (d >= -deadzone)) { 
	motor(motord,0); 
      }
      else {
	if (d < 0) { 
	  d = d + 28;
	  motor(motord,d);
	}
	else {
	  d = d - 27;
	  motor(motord,d);
	}
	
      }
    }




    ao();           /* turn all motors off */

  }

}