{"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 There are a group of students. Some of them may know each other, while others don\u0027t. For example, A and B know each other, B and C know each other. But this may not imply that A and C know each other. \n \u003cbr\u003e \n \u003cbr\u003eNow you are given all pairs of students who know each other. Your task is to divide the students into two groups so that any two students in the same group don\u0027t know each other.If this goal can be achieved, then arrange them into double rooms. Remember, only paris appearing in the previous given set can live in the same room, which means only known students can live in the same room. \n \u003cbr\u003e \n \u003cbr\u003eCalculate the maximum number of pairs that can be arranged into these double rooms. \n \u003cbr\u003e \n\u003c/div\u003e\n\u003cbr\u003e有n个关系,他们之间某些人相互认识。这样的人有m对。\n\u003cbr\u003e你需要把人分成2组,使得每组人内部之间是相互不认识的。\n\u003cbr\u003e如果可以,就可以安排他们住宿了。安排住宿时,住在一个房间的两个人应该相互认识。\n\u003cbr\u003e最多的能有多少个房间住宿的两个相互认识。"}},{"title":"Input","value":{"format":"HTML","content":"For each data set: \n\u003cbr\u003eThe first line gives two integers, n and m(1\u0026lt;n\u0026lt;\u003d200), indicating there are n students and m pairs of students who know each other. The next m lines give such pairs. \n\u003cbr\u003e \n\u003cbr\u003eProceed to the end of file. \n\u003cbr\u003e有多少测试数据\n\u003cbr\u003e每组测试数据,第一行两个整数n和m。\n\u003cbr\u003e接下来m行,每行两个整数,表示一对认识的人。\n"}},{"title":"Output","value":{"format":"HTML","content":"If these students cannot be divided into two groups, print \"No\". Otherwise, print the maximum number of pairs that can be arranged in those rooms. \n\u003cbr\u003e\n\u003cbr\u003e如果不能分成两组,输出No\n\u003cbr\u003e如果可以,输出最多有多少个房间内两个人是相互认识。"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre\u003e4 4\n1 2\n1 3\n1 4\n2 3\n6 5\n1 2\n1 3\n1 4\n2 5\n3 6\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre\u003eNo\n3\u003c/pre\u003e"}}]}