int i;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:

   for(i=0;i<10;i++) {
      Serial.print(i);
      Serial.println();
      delay(99);
   }

   for(i=10;i>0;i--) {
      Serial.println(i);
      delay(99);
   }

}