#include <iostream>
#include <cstdlib>
using namespace std;
int main ()
{
int n,i;
double sum=0,minus,total,j;
    cout<<"請輸入一個正整數,以計算1/1-1/2+1/3-1/4+....+1/n: "<<endl;
    cin>>n;
    for(i=1;i<=n;i++)
    {
        j=i/2;
        if(j-(int)j==0)
        {
        minus=1/j;
        }
        else
        minus=0;

        sum=sum+1/i-2*minus;


                     }
cout<<"總合為:"<<sum<<endl;
system("pause");
return 0;

    }