#include <stdio.h>

int main() {
    double x2 = 1.0;
    double x3 = 0.0;
    double x4 = 1.0;
    while (x4 < 10000) {
        x3 += 1/(x4*x4);
        x4++;
    }
    printf("%f\n",x3);
    return 0;
}