Int F1(int x)
{
    If x is even then
       return x/2;
    else
       return F1(F1(3x+1));
}

Int F2(int x, int y)
{
    If y=0 then
      return x;
    else
      return F2(y, x mod y);
}

Int F3(int x)
{
    Int p, q;

    If x <= 2 then
      return x;
    else
      p=F3(x-2);
      q=F3(x-3);
      return p+q;
}