{"trustable":true,"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":"\u003cdiv class\u003d\"panel_content\"\u003e北方已经进入寒冬,白行者们即将到来。一名年轻的守夜人站在城墙上。\u003cbr\u003e这名年轻的守夜人想出了一个方法来保暖。每次他独立且均匀地生成一个在范围$[l_i, r_i]$内的随机有理数x,然后向东走x米。\u003cbr\u003e现在他有n个范围$[l_1, r_1], [l_2, r_2] ... [l_n, r_n]$,他想知道到原点的期望距离。如果答案是一个分数$\\frac{p}{q}$,请输出一个整数$0 \\leq s \u0026lt; 998244353$,使得$p \\equiv sq~(mod~998244353)$。\u003c/div\u003e"}},{"title":"输入","value":{"format":"HTML","content":"第一行包含一个整数n。$1 \\leq n \\leq 15$\u003cbr\u003e接下来的n行,每行包含两个整数$l_i, r_i$。$(-10^6 \\leq l_i \\leq r_i \\leq 10^6)$"}},{"title":"输出","value":{"format":"HTML","content":"在一行中输出到原点的期望距离,取模998244353。\u003cbr\u003e"}},{"title":"示例","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\r\n-2 3\r\n-2 1\r\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e199648872\r\n\r\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e"}}]}