int trig=3;
int echo=2;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(trig, OUTPUT);
pinMode(echo, INPUT)
digitalWrite(trig, LOW);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(trig, HIGH);
delayMicroseconds(10);    //enviar pulsos de 10s
digitalWrite(trig, LOW);
unsigned long tiempo=pulseIn(echo,HIGH);// recuperara tiempo
int dist=tiempo/59;
Serial.print("distancia: ");
Serial.print(dist);
Serial.print("cm");
Serial.print();
delay(100);
}



void avanzar (int velocidad)