#include <stdio.h>
#include <math.h>
#include <iostream>
using namespace std;
int main()
{
double arr[101];
double asd=0;
for (int i=1;i<=100;i++)
{
arr[i]=1/pow(i, 2);
asd+=arr[i];
}
cout<<asd<<endl;
return 0;
}
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