Step Motor - Serial step controlled

hi, i'm working on project need control step motor serial monitor,
what i've done far doesn't seen work, stepper move number of steps with
one digit number (0 - 9), , if try use more one, program sums digits, example, if type 12, move 3 steps.

also, can't use negative numbers apparently.

please help!

#include <stepper.h>
#include <stdlib.h>
#define steps 200
stepper motor(steps, 8, 9, 10, 11);
int i=0, g;
char ascii[10];
void setup() {
  serial.begin(9600);
  motor.setspeed(1);

}

void loop() {
 
  if(serial.available() > 0){
    for(i=0;i<10;i++){
      ascii=serial.read();
      if((ascii!='-')&&(ascii!='.')&&(ascii!='0')&&(ascii!='1')&&(ascii!='2')&&(ascii!='3')&&(ascii!='4')&&(ascii!='5')&&(ascii!='6')&&(ascii!='7')&&(ascii!='8')&&(ascii!='9')){
      ascii='\0';
    }
    //int g = atoi(ascii);
    int g = atoi(ascii);
    motor.step(g);
  }
}

example 4 of serial input basics shows how read multi digit number serial port. 

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