Module: For 循环语句。典型任务


Problem

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结束行数字 - 1

Problem

给定一个自然数 N。编写一个程序来计算以下表达式的前 N 个因子：
\(P = {2 \over 3}\cdot{4 \over 5}\cdot{6 \over 7}\ cdot ... \cdot {{2 \cdot N} \over {2\cdot N +1}}\)

输入
输入是一个自然数N。

印记
输出问题的答案
 

 

例子
<头> <正文>

time 1000 ms
memory 256 Mb
Rules for program design and list of errors in automatic problem checking

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# 输入 输出
1 42 0.135542