{"trustable":false,"prependHtml":"\u003cstyle type\u003d\u0027text/css\u0027\u003e\n .input, .output {\n border: 1px solid #888888;\n }\n .output {\n margin-bottom: 1em;\n position: relative;\n top: -1px;\n }\n .output pre, .input pre {\n background-color: #EFEFEF;\n line-height: 1.25em;\n margin: 0;\n padding: 0.25em;\n }\n \u003c/style\u003e\n \u003clink rel\u003d\"stylesheet\" href\u003d\"//codeforces.org/s/96598/css/problem-statement.css\" type\u003d\"text/css\" /\u003e\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 type\u003d\"text/javascript\" async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS_HTML-full\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"MD","content":"一天水原遨游在数学的海洋中,突然他的面前出现了n组数,第i组数有m_i个数,水原定义了一种规则,如果一个数k出现在两个不同的组中,那这两个不同的组就可以通过k这个数相连,现在水原想找到其中n-1个这样的关系是的这n组数相互连通。"}},{"title":"Input","value":{"format":"MD","content":"第一行一个整数n,(2≤n≤2·10^5)。\n接下来n行,每行有一个整数m(1≤m≤2·10^5)代表这一组中有多少个数,然后接着有m个整数d_1,d_2……d_m(1≤di≤10^9)\n所有数加起来不超过2e5个"}},{"title":"Output","value":{"format":"MD","content":"如果可以有这样的关系使它们相连,则输出n-1行,每行3个整数,分别是a、b、k,代表a组和b组通过k这个数相连。\n如果不行,输出\"impossible\""}},{"title":"Examples","value":{"format":"MD","content":"\u003cdiv class\u003d\"sample-test\"\u003e\n \u003cdiv class\u003d\"input\"\u003e\n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e\n \u003cpre\u003e6\n2 17 10\n1 5\n2 10 22\n3 17 22 9\n2 17 8\n3 9 22 16\n\u003c/pre\u003e\n \u003c/div\u003e\n \u003cdiv class\u003d\"output\"\u003e\n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e\n \u003cpre\u003eimpossible\n\u003c/pre\u003e\n \u003c/div\u003e\n \u003cdiv class\u003d\"input\"\u003e\n \u003cdiv class\u003d\"title\"\u003e\n Input\n \u003c/div\u003e\n \u003cpre\u003e6\n2 17 10\n2 5 10\n2 10 22\n3 17 22 9\n2 17 8\n3 9 22 16\n\u003c/pre\u003e\n \u003c/div\u003e\n \u003cdiv class\u003d\"output\"\u003e\n \u003cdiv class\u003d\"title\"\u003e\n Output\n \u003c/div\u003e\n \u003cpre\u003e1 4 17\n4 3 22\n3 2 10\n4 6 22\n1 5 17\n\u003c/pre\u003e\n \u003c/div\u003e\n\u003c/div\u003e"}}]}