C++ Program to take log^n

Statement:

C++ program to take log^n

Code : 

#include<iostream>

using namespace std;

void main()

{

       int i, n, s = -1;

       float sum = 0;

       cout << "Enter The Value Of n : ";

       cin >> n;

       for (i = 1; i <= n; i++)

       {

              s = s * -1;

              sum += s*1.0 / i;

       }

       cout << "Log Of 2 : " << sum;

       cout << "\n\n";

       system("pause");

}