33: calculates the value of the score addition and subtraction expression. 33 indicates the expression.

33: calculates the value of the score addition and subtraction expression. 33 indicates the expression.
33: calculate the value of the score addition and subtraction expression

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Total time limit:

1000 ms

 

Memory limit:

65536kB

Description

Write a program and enter the value of n to calculate 1/1-1/2 + 1/3-1/4 + 1/5-1/6 + 1/7-1/8 +... + (-1) n-1 · 1/n value.

Input

Enter a positive integer n. 1 <= n <= 1000.

Output

Output a real number, which is the value of the expression and is retained to the fourth digit after the decimal point.

Sample Input

2

Sample output

0.5000

 1 e<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<cmath> 5 using namespace std; 6 int main() 7 { 8     int n; 9     cin>>n;10     double tot=0;11     double fm=1; 12     for(int i=1;i<=n;i++)13     {14         if(i%2==0)15         {16             tot=tot-(1/fm);17             fm++;18         }    19         else 20         {21             tot=tot+(1/fm);22             fm++;23         }24     }25     printf("%.4lf",tot);26     return 0;27 }