{"trustable":false,"sections":[{"title":"","value":{"format":"HTML","content":"每个在圣巢的容器骑士都会希望成为最纯粹的容器。在 N (1 \u0026lt;\u003d N \u0026lt;\u003d 10,000) 个骑士里, 给定M (1 \u0026lt;\u003d M \u0026lt;\u003d 50,000) 个有序数对 (A, B)表示A认为B是纯粹的. 这种关系具有传递性, 如果A认为B是纯粹的,B认为C是纯粹的,那么A就认为C是纯粹的。被其他所有骑士都认定为纯粹的骑士,就将成为纯粹容器。"}},{"title":"Input","value":{"format":"HTML","content":"第一行给定两个整数N和M\n接下来的M行,每行两个整数A和B,表示A认为B是纯粹的。"}},{"title":"Output","value":{"format":"HTML","content":"输出有多少个纯粹容器。"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003e3 3\n1 2\n2 1\n2 3\n\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003e1\n\u003c/pre\u003e"}},{"title":"Hint","value":{"format":"HTML","content":"3号骑士是唯一的一个纯粹骑士"}}]}