{"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":"\u003cdiv\u003e \n \u003cspan\u003ePear和Fish正在进行这样一个游戏:\u003c/span\u003e\n\u003c/div\u003e \n\u003cdiv\u003e\n 一个袋子里一开始装着w个白球和b个黑球。从Pear开始,每次轮流随机抽出一个球。如果抽出的球是白色的,则抽出这个球的人立即获胜。每当一个球被取出后(然后结算获胜情况后),会有另一个球自动滚出来(不算任何人抽的)。每个人抽球、和自动滚出来的球都是等概率的。那么Pear获胜率是多少呢?\n\u003c/div\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003e \u003cspan\u003e两个数w\u003c/span\u003e,\u003cspan\u003eb含义如上。w\u003c/span\u003e,b\u0026lt;\u003d1000\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003e \u003cspan\u003ePear获胜的概率,保留至少10位小数。\u003c/span\u003e\u003c/p\u003e"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cp\u003e Input 1:\u0026nbsp;\u003c/p\u003e \n\u003cp\u003e 1 3\u003c/p\u003e \n\u003cp\u003e Input 2:\u003c/p\u003e \n\u003cp\u003e 5 5\u003c/p\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cp\u003e Output 1:\u003c/p\u003e \n\u003cp\u003e 0.500000000\u003c/p\u003e \n\u003cp\u003e Output 2:\u003c/p\u003e \n\u003cp\u003e 0.658730159\u003c/p\u003e"}}]}