경우의수를 다 풀엇던데 너무 많아서 경로 찍어드릴께여
http://kin.naver.com/qna/detail.nhn?d1id=11&dirId=1113&docId=146648180&qb=OTE5IC0gOTIxIC0gODkzIC0gMjc5IC0gNDM2IC0gPz8/&enc=utf8§ion=kin&rank=3&search_sort=0&spq=0&pid=g2Vmwc5Y7tNssblFKbhssc--268731&sid=T2shwGLqak8AAGgnHZM