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分数矩阵

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 12230    Accepted Submission(s): 6803


Problem Description
我们定义如下矩阵:
1/1 1/2 1/3
1/2 1/1 1/2
1/3 1/2 1/1
矩阵对角线上的元素始终是1/1，对角线两边分数的分母逐个递增。
请求出这个矩阵的总和。
 

Input
每行给定整数N (N<50000)，表示矩阵为 N*N.当N为0时，输入结束。
 

Output
输出答案，保留2位小数。
 

Sample Input
1
2
3
4
0
 

Sample Output
1.00
3.00
5.67
8.83
 

Author
Wiskey
 

Source
2008信息工程学院集训队——选拔赛
 

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