HW1_sum

#define _USE_MATH_DEFINES

#include <cstdio>
#include <cmath>


int main(){
    int n = 0;
    scanf("%d", &n);
    double sum = 0.0, sum1 = 0.0, goodsum = M_PI*M_PI/6;
    for (int i = 1; i <= n; ++i){
        sum += (1.0 / i/i);
        sum1 += (1.0 / (n - i + 1)/(n - i + 1));
    }

    printf("%.20f\n%.20f\n%.20f\n", sum, sum1, goodsum);
    return 0;
}