{"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\n\u003cscript\u003e\n window.katexOptions \u003d {\n delimiters: [\n {left: \u0027$$$$$$\u0027, right: \u0027$$$$$$\u0027, display: true},\n {left: \u0027$$$\u0027, right: \u0027$$$\u0027, display: false},\n {left: \u0027$$\u0027, right: \u0027$$\u0027, display: true},\n {left: \u0027$\u0027, right: \u0027$\u0027, display: false}\n ]\n };\n\u003c/script\u003e\n","sections":[{"title":"","value":{"format":"HTML","content":"\tVasya 有n块蛋糕准备自己吃并且每天吃掉K块蛋糕,Petya决定偷吃Vasya的蛋糕。为了不让她发现他每次只偷吃剩下的10%。\n\t注意的是,因为是吃自己的蛋糕所以如果剩下的蛋糕不足K块,Vasya就会吃完。而因为是偷吃别人的蛋糕,所以能吃少点就少点,比如,如果剩下86块蛋糕,Petya只会吃掉8块。而如果剩下的不满10块,比如8块,那Petya就不吃。\n\t如果Vasya吃到了蛋糕总量的至少一半,她就不会发现Petya的偷吃行为。请你求出最小的K,使Vasya不会发现Petya偷吃。\n\t\u003cstyle type\u003d\u0027text/css\u0027\u003e .input, .output {border: 1px solid #888888;} .output {margin-bottom:1em;position:relative;top:-1px;} .output pre,.input pre {background-color:#EFEFEF;line-height:1.25em;margin:0;padding:0.25em;} .title {background-color:#FFFFFF;border-bottom: 1px solid #888888;font-family:arial;font-weight:bold;padding:0.25em;} \u003c/style\u003e \u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n\t MathJax.Hub.Config({\n\t tex2jax: {inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027]], displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027]]}\n\t });\n\t \u003c/script\u003e\n\t \u003cscript type\u003d\"text/javascript\" async\n\t src\u003d\"https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\"\u003e\n\t \u003c/script\u003e\n\t\u003cp\u003eAfter passing a test, Vasya got himself a box of n candies. He decided to eat an equal amount of candies each morning until there are no more candies. However, Petya also noticed the box and decided to get some candies for himself.\u003c/p\u003e\n\t\u003cp\u003eThis means the process of eating candies is the following: in the beginning Vasya chooses a single integer k, same for all days. After that, in the morning he eats k candies from the box (if there are less than k candies in the box, he eats them all), then in the evening Petya eats 10% of the candies in the box. If there are still candies left in the box, the process repeats\u0026nbsp;— next day Vasya eats k candies again, and Petya\u0026nbsp;— 10% of the candies left in a box, and so on.\u003c/p\u003e\n\t\u003cp\u003eIf the amount of candies in the box is not divisible by 10 , Petya rounds the amount he takes from the box down. For example, if there were 97 candies in the box, Petya would eat only 9 of them. In particular, if there are less than 10 candies in a box, Petya won\u0027t eat any at all.\u003c/p\u003e\n\t\u003cp\u003eYour task is to find out the minimal amount of k that can be chosen by Vasya so that he would eat at least half of the n candies he initially got. Note that the number k must be integer.\u003c/p\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003eThe first line contains a single integer n (1 \u003c\u003dn \u003c\u003d 10^{18})\u0026nbsp;— the initial amount of candies in the box.\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003eOutput a single integer\u0026nbsp;— the minimal amount of k that would allow Vasya to eat at least half of candies he got.\u003c/p\u003e"}},{"title":"Example","value":{"format":"HTML","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\u003e68\u003cbr\u003e\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\u003cbr\u003e\u003c/pre\u003e\n \u003c/div\u003e\n\u003c/div\u003e"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003eIn the sample, the amount of candies, with k\u003d3, would change in the following way (Vasya eats first):\u003c/p\u003e\n\u003cp\u003e68 \\to 65 \\to 59 \\to 56 \\to 51 \\to 48 \\to 44 \\to 41 \\\\ \\to 37 \\to 34 \\to 31 \\to 28 \\to 26 \\to 23 \\to 21 \\to 18 \\to 17 \\to 14 \\\\ \\to 13 \\to 10 \\to 9 \\to 6 \\to 6 \\to 3 \\to 3 \\to 0.\u003c/p\u003e\n\u003cp\u003eIn total, Vasya would eat 39 candies, while Petya\u0026nbsp;— 29.\u003c/p\u003e"}}]}