const int in_1=10;
const int in_2=9;
const int en=11;

void setup() 
{
  pinMode(in_1, OUTPUT);
  pinMode(in_2, OUTPUT);
  pinMode(en, OUTPUT);
  // put your setup code here, to run once:

}

void loop() {
  analogWrite(en,255);
  digitalWrite(in_1, HIGH);
  digitalWrite(in_2, LOW);
  delay(3000);
  digitalWrite(in_1, HIGH);
  digitalWrite(in_2, HIGH);
  delay(1000);
  digitalWrite(in_1, LOW);
  digitalWrite(in_2, HIGH);
  delay(3000);
  digitalWrite(in_1, HIGH);
  digitalWrite(in_2, HIGH);

  // put your main code here, to run repeatedly:

}