Test.java

package com.godoro;

public class Test {

  static int step(int totalSteps, int currentSteps, int currentPosibilities) {
    if (currentSteps == totalSteps) {
      return currentPosibilities;
    } else if (currentSteps == totalSteps - 1) {
      return currentPosibilities + 1;
    } else if (currentSteps == totalSteps - 2) {
      return currentPosibilities + 2;
    } else {
      return step(totalSteps, currentSteps + 1, currentPosibilities )
              + step(totalSteps, currentSteps + 2, currentPosibilities );
    }
  }
  
  public static void main(String[] args) {
    int totalSteps=20;
    int posibilities=step(totalSteps,0,0);
    System.out.println(posibilities);
  }
}