{"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":"今天明珠小姐姐收到了水原的组队邀请。\n\n是要做恋人节任务吗?\n\n是要带我坐飞行坐骑遨游艾欧泽亚吗?\n\n在明珠小姐姐胡思乱想的时候,耳边响起叮的一声。\n\n“这个本差T差好久了,快按出发。“\n\n明珠小姐姐面无表情地打完了本,由于副本的性质,只能拿走一样物品,于是她决定从水原手上抢走稀有度最高的掉落物。\n\n现在已知这 n 件物品的稀有度,那么能否通过至多一次的区间反转来让这 n 件物品按照非递减顺序来排序呢?\n\n仍然交给你来解决啦!"}},{"title":"Input","value":{"format":"MD","content":"输入为两行,第一行为一个整数 n (1 ≤ n ≤ 10^6),表明掉落物的总数。\n\n第二行为 n 个整数 ai (1 ≤ ai ≤ 10^9), 表明掉落物的稀有度。"}},{"title":"Output","value":{"format":"MD","content":"输出为一行,包含两个整数,如果可以通过至多一次的区间反转来让这n件物品按照非递减顺序来排序,那么输出这个翻转区间的两个端点标号,否则则输出\"impossible\"(不含引号)\n\n如果有多解,输出任何一个即可。"}},{"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\u003e7\n10 13 19 19 15 14 20\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\u003e3 6\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\n9 1 8 2 7 3\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\u003e3\n1 2 3\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 1\n\u003c/pre\u003e\n \u003c/div\u003e\n\u003c/div\u003e"}}]}