#define PIN_TRIG 3
#define PIN_ECHO 2
#define Red 7

void setup() {
  Serial.begin(9600);
  delay(1000);
  pinMode(PIN_TRIG, OUTPUT);
  pinMode(PIN_ECHO, INPUT);
  pinMode(Red, OUTPUT);
}

void loop() {
  digitalWrite(PIN_TRIG, HIGH);
  delay(100);
  digitalWrite(PIN_TRIG, LOW);

  int duration = pulseIn(PIN_ECHO, HIGH);
  int distance =(duration / 2) / 29.1;
  Serial.print("Distance in CM: ");
  Serial.println(distance);
  
if ( distance > 25 ) {
  digitalWrite(Red, HIGH);
}
else {
  digitalWrite(Red, LOW);
}
}