const int M1 = 26;
const int M2 = 27;
const int M3 = 33;
const int M4 = 12;

const int trigPin = 14;
const int echoPin = 5;
long duration;
int distance;

void setup() {
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(M1, OUTPUT);
  pinMode(M2, OUTPUT);
  pinMode(M3, OUTPUT);
  pinMode(M4, OUTPUT);
}

void Forward() {
  digitalWrite(M1, HIGH);
  digitalWrite(M2, LOW);
  digitalWrite(M3, HIGH);
  digitalWrite(M4, LOW);
}

void Stop() {
  digitalWrite(M1, LOW);
  digitalWrite(M2, LOW);
  digitalWrite(M3, LOW);
  digitalWrite(M4, LOW);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println("  cm");
  delay(100);
  if (distance > 7) {
    Forward();
  } 
  else {
    Stop();
  }
}