/*
Задание 2.
*/

#include <cmath>
#include <iomanip>
#include <iostream>

using namespace std;

int main() {
    size_t n;
    cin >> n;

    if (n == 0) {
        cout << "The division by 0 operation is not possible";
        return 0;
    }

    double result = 0;
    double sin_sum = 0;
    for (int i = 1; i <= n; ++i) {
        sin_sum += sin(i);
        result += cos(i) / sin_sum;
    }

    const int PRECISION = 15;
    cout << fixed << setprecision(PRECISION) << result;

    return 0;
}