#define ECHO_PIN 20
#define TRIG_PIN 21

void setup() {
  pinMode(33, OUTPUT);
  pinMode(26, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}

float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  float distance = readDistanceCM();
  if (distance<100){
   digitalWrite(26, HIGH);
   digitalWrite(33, LOW);
  }else{
   digitalWrite(26, LOW);
   digitalWrite(33, HIGH);
  }
}