#define ultra=12
#define u=13
void setup() {
  // put your setup code here, to run once:
pinMode(12, OUTPUT);
Serial.begin(9600);
pinMode(13, INPUT);
}
float readdictance()
{
  digitalWrite(12, LOW);
  delayMicroseconds(2);
  digitalWrite(12, HIGH);
  delayMicroseconds(10);
  digitalWrite(12, LOW);\
  int duration=pulseIn(13,HIGH);
  return duration*0.034/2;
}

void loop() {
  // put your main code here, to run repeatedly:
int f =readdictance();
Serial.println(f);
delay(100);
}