{"trustable":false,"sections":[{"title":"","value":{"format":"MD","content":"有N(N\u003c\u003d10000)头牛,每头牛都想成为most poluler的牛,给出M(M\u003c\u003d50000)个关系,如(1,2)代表1欢迎2,关系可以传递,但是不可以相互,即1欢迎2不代表2欢迎1,但是如果2也欢迎3那么1也欢迎3.\n给出N,M和M个欢迎关系,求被所有牛都欢迎的牛的数量。"}},{"title":"Input","value":{"format":"MD","content":"第一行N,M\n接下来M行A,B,表示A欢迎B"}},{"title":"Output","value":{"format":"MD","content":"一个数,表示答案"}},{"title":"Sample Input","value":{"format":"MD","content":"3 3\n1 2\n2 1\n2 3\n"}},{"title":"Sample Output","value":{"format":"MD","content":"1\n"}}]}