{"trustable":false,"prependHtml":"\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\" type\u003d\"text/javascript\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"\u003cscript type\u003d\u0027text/x-mathjax-config\u0027\u003eMathJax.Hub.Config({tex2jax: { inlineMath: [[\u0027$\u0027,\u0027$\u0027]] } }); \u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027 src\u003d\u0027https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\u0027\u003e\u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027\u003esetTimeout(function(){MathJax.Hub.Queue([\u0027Typeset\u0027, MathJax.Hub, \u0027left_view\u0027]);}, 2000);\u003c/script\u003e\n\u003cdiv class\u003d\"panel_content\"\u003e\n小明正在看乒乓球比赛,比赛规则是每场比赛两个人对打,每两个人之间最多打一场比赛。\n \u003cbr\u003e球赛的规则如下:\n \u003cbr\u003e如果A打败了B,B又打败了C,而A与C之间没有进行过比赛,那么就认定,A一定能打败C。\n \u003cbr\u003e如果A打败了B,B又打败了C,而且,C又打败了A,那么A、B、C三者都不可能成为冠军。\n \u003cbr\u003e根据这个规则,无需循环较量,或许就能确定冠军。你的任务就是面对一群比赛选手,在经过了若干场撕杀之后,确定是否已经实际上产生了冠军。\n \u003cbr\u003e\n\u003c/div\u003e"}},{"title":"Input","value":{"format":"HTML","content":"输入含有一些选手群(多组输入),每群选手都以一个整数n(n\u0026lt;1000)开头,后跟n对选手的比赛结果,比赛结果以一对选手名字(中间隔一空格)表示,前者战胜后者。如果n为0,则表示输入结束。\n\u003cbr\u003e"}},{"title":"Output","value":{"format":"HTML","content":"对于每个选手群,若你判断出产生了冠军,则在一行中输出“Yes”,否则在一行中输出“No”。\n\u003cbr\u003e"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre\u003e3\nAlice Bob\nSmith John\nAlice Smith\n5\na c\nc d\nd e\nb e\na d\n0\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre\u003eYes\nNo\u003c/pre\u003e"}}]}