int trig=12;
int echo=4;
void setup()
{
  pinMode(trig,OUTPUT);
  pinMode(echo,INPUT);
  Serial.begin(9600);
}
void loop()
{
  digitalWrite(trig,LOW);
  delay(10);
  digitalWrite(trig,HIGH);
  delay(10);
  digitalWrite(trig,LOW);
  float duration=pulseIn(echo,HIGH);
  float distance=(0.017*duration);
  delay(1000);
  Serial.print(distance);
}