#include <iostream>
#include <math.h>
using namespace std;

int main()
{
    int i, n;
    float sum = 0;

    cout << "Enter the value of n: ";
    cin >> n;

    for (i=1; i<=n; i++)
        sum += 1.0/pow(i,2);

    cout << "Sum: " << sum;


    return 0;
}

for (i=1; i<=n; i++)
    sum += pow(2,-i);