#include <Stepper.h>

const int stepPerRevolution = 200;

Stepper myStepper(stepPerRevolution, 18, 19, 20 ,21);

void setup() {
 myStepper.setSpeed(60);
}

void loop() {
 myStepper.step(50);
 delay(500);

 myStepper.step(50);
 delay(500);

  myStepper.step(50);
 delay(500);

 myStepper.step(50);
 delay(500);

 myStepper.step(-50);
 delay(500);
}