#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cout << #x << ": " << x << '\n';
#define double long double
signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif

    double ans = 0;
    double x;
    cin >> x;

    auto sinc = [] (double x) {
        if (x == 0)
            return (double)1.;
        else
            return sinl(x)/x;
    };

    for (; x < 1e6; ++x) {
        auto t = sinc(x);
        ans += t * t;
    }   

    ans += 1. / (2 * x);

    cout.precision(20);
    cout << fixed;
    cout << ans << endl;
}