{"trustable":false,"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":"N个物品,每次得到第i个物品的概率为pi,而且有可能什么也得不到,问期望多少次能收集到全部N个物品"}},{"title":"Input","value":{"format":"HTML","content":"1\u003c\u003dN\u003c\u003d20\np1+...+pN \u003c\u003d1\n多组数据,每组数据第一行为N,第二行为p1-pN"}},{"title":"Output","value":{"format":"HTML","content":"对于每组数据输出答案\n误差不得超过1e-4"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre\u003e1\n0.1\n2\n0.1 0.4\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre\u003e10.000\n10.500\u003c/pre\u003e"}},{"title":"Hint","value":{"format":"HTML","content":""}}]}