{"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":"喜羊羊最近身边人都脱单了,所以他馋了,想找一个女朋友,最近一直去教学楼自习,这一天他遇到一个漂亮学姐,可他胆子小,不敢要人家联系方式,可他抑制不住内心的躁动,终于还是去了,学姐也非常大气的给了她qq号,喜羊羊正在疑惑为什么如此简单的就要到了;打开手机qq一看,原来是需要回答一个问题才能加上学姐: 已知函数:f(n) \u003d ∑ [(-1)^i] * i(i从1到n) ;现在给你一个n,需要算出函数的值,答案正确才能加上qq,喜羊羊非常喜欢这个女生,可是他数学非常菜(装的),不会算,聪明的你能帮帮他吗?"}},{"title":"Input","value":{"format":"MD","content":"输入一个数n (1 ≤ n ≤ 10^15)."}},{"title":"Output","value":{"format":"MD","content":"输出一个数,即f(n)的值"}},{"title":"Examples","value":{"format":"MD","content":"Input\n4\nOutput\n2\nInput\n5\nOutput\n-3"}},{"title":"Note","value":{"format":"MD","content":"样例解释:\nf(4) \u003d - 1 + 2 - 3 + 4 \u003d 2\n\nf(5) \u003d - 1 + 2 - 3 + 4 - 5 \u003d - 3\n\n注意: n可能比较大,数据范围用long long\n\n"}}]}