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Problem1231--1.12:04-分数求和

1231: 1.12:04-分数求和

Time Limit: 1 Sec  Memory Limit: 128 MB  Submit: 2  Solved: 1
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Description

S=1/2+1/6+1/12+1/20+1/30+1/42+... 求数列前n项和，答案保留2位小数


Input

整数n 

Output

一个浮点数

Sample Input Copy 

10

Sample Output Copy 

0.91

HINT

1<=n<=100

Source/Category

算法 基础 
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