int ENA = 5;
int in1 = 7;
int in2 = 8;

void setup(){
  pinMode(ENA, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  analogWrite(ENA, HIGH);
}

void loop() {
  digitalWrite(in1, LOW);
  digitalWrite(in2, HIGH);
  delay(1000);
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
  delay(1000);
}