{"trustable":true,"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$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript type\u003d\"text/javascript\" async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS_HTML-full\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"\u003cp\u003e将$$$N$$$个点排列成一个圆形,中间放置一个点固定为根节点,问特殊生成树的种类数。\u003c/p\u003e\u003cp\u003e特殊生成树:除根节点以外,其他节点只能与自己左右节点相连,或与根节点相连。\u003c/p\u003e\u003cp\u003ep.s.若节点的左右节点为同一个节点,向左或向右连接视为不同的生成树。\u003c/p\u003e\u003cp\u003e由于种类数可能过大,对$$$1,000,000,007$$$取模。\u003c/p\u003e\u003cp\u003e当$$$N\u003d3$$$时,所有生成树表示如下:\u003c/p\u003e\u003cp\u003e\u003cimg class\u003d\"tex-graphics\" src\u003d\"CDN_BASE_URL/a6519863aaa680c06f59b9ad528526f9?v\u003d1715424981\" style\u003d\"max-width: 100.0%;max-height: 100.0%;\"\u003e\u003c/p\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003e多组数据,请输入要文件结束。\u003c/p\u003e\u003cp\u003e每组数据包含一个整数$$$N(0 \u0026lt; N \u0026lt; 10^9)$$$。\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003e对于每组数据,输出一个整数,表示特殊生成树的种类数,答案对$$$1,000,000,007$$$取模。\u003c/p\u003e"}},{"title":"Examples","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003e2\n3\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e5\n16\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}}]}