static int ff(int f[], int g[], int i, int n, int r) {
    if (i > n)
      return f[r];
    else {
      if (i % 2 == 1)
        f[r] = f[r-2] - g[r-1] + f[1] - g[0];
      else
        f[r] = -f[r-1] + g[r-1] - g[r-2] - f[0] + g[0];
      g[r] = 2*g[r-1] - 2*f[0] + g[1];
      for (int j = 0; j < r; j++) {
        f[j] = f[j+1];
        g[j] = g[j+1];
      }
      return ff(f, g, i+1, n, r);
    }
  }

  static int fRec2(int n, int r) {
    int f[] = new int[maxR + 1];
    int g[] = new int[maxR + 1];
    if (n < r)
      return 2;
    else {
      for (int j = 0; j < r; j++) {
        f[j] = 2;
        g[j] = -1;
      }
      return ff(f, g, r, n, r);
    }
  }

  // (c) iterativno
  static int fIter(int n, int r) {
    int f[] = new int[maxR + 1];
    int g[] = new int[maxR + 1];
    for (int i = 0; i < r; i++) {
      f[i] = 2;
      g[i] = -1;
    }
    if (n < r)
      return f[n];
    else {
      for (int i = r; i <= n; i++) {
        if (i % 2 == 1)
          f[r] = f[r-2] - g[r-1] + f[1] - g[0];
        else
          f[r] = -f[r-1] + g[r-1] - g[r-2] - f[0] + g[0];
        g[r] = 2*g[r-1] - 2*f[0] + g[1];
        for (int j = 0; j < r; j++) {
          f[j] = f[j+1];
          g[j] = g[j+1];
        }
      }
    }
    return f[r];
  }