{"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$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\" type\u003d\"text/javascript\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"MD","content":"\u003cscript type\u003d\u0027text/x-mathjax-config\u0027\u003eMathJax.Hub.Config({tex2jax: { inlineMath: [[\u0027$\u0027,\u0027$\u0027]] } }); \u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027 src\u003d\u0027https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\u0027\u003e\u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027\u003esetTimeout(function(){MathJax.Hub.Queue([\u0027Typeset\u0027, MathJax.Hub, \u0027left_view\u0027]);}, 2000);\u003c/script\u003e\n\u003cdiv class\u003d\"panel_content\"\u003e\n 筷子先生对随机现象感兴趣,他进行了一项研究随机性的实验。在这个实验中,他将n个球投掷到m个盒子中,每个球有相同的概率到达每个盒子。实验后,他计算了统计方差 V\n \u003cbr\u003e $$V\u003d\\frac{\\sum_{i\u003d1}^{m}(X_{i}-\\bar X)^{2}}{m}$$ \n \u003cbr\u003e$X_{i}$是第i个盒子中的球的数量,而$\\bar X$是盒子中球的平均数量。 \n \u003cbr\u003e你的任务是找出V的期望值。\n \u003cbr\u003e \n\u003c/div\u003e"}},{"title":"Input","value":{"format":"MD","content":"有多组输入,每组包含两个数n,m(1\u003c\u003dn,m\u003c\u003d1e9),输入以n\u003d0,m\u003d0结束.\n\u003cbr\u003e"}},{"title":"Output","value":{"format":"MD","content":"每组输出A/B,A/B为不可约分数,如果答案为整数,那么让B为1."}},{"title":"Sample Input","value":{"format":"MD","content":"\u003cpre\u003e2 1\n2 2\n0 0\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"MD","content":"\u003cpre\u003e0/1\n1/2\n\n\n \n \u003ci style\u003d\"font-size:1px\"\u003e \u003c/i\u003e\u003c/pre\u003e"}},{"title":"Hint","value":{"format":"MD","content":"\u003cpre\u003e\n在第二组样例中,有4中可能的结果,两种结果V\u003d0,还有两种结果V\u003d1.\n \u003c/pre\u003e"}}]}