Starting at the origin O, a point W walks in either positive or negative direction  with incrementing absolute step sizes of 1,2,3,…, 2005. In other words, the point W walks (+1 or –1 step )from the origin, then (+2 or –2 steps) from the last point,…,and finally (+2005 or –2005 steps) from the last point .     Prove that the point W can not be at the origin after finishing 2005 walks.