#include <bits/stdc++.h>

using namespace std;
using ull = unsigned long long;
using ll = long long;
using lli = long long int;
using ld = long double;
using pa = pair<int, int>;
using ppa = pair<pa, int>;
#define SORT(v, n) sort(v, v + n);
#define ALL(v) v.begin(), v.end()
#define VSORT(v) sort(ALL(v))
#define GRESORT(v) sort(ALL(v), greater<ll>())
#define REVERSE(v) reverse(ALL(v))
#define overlap(v) v.erase(unique(ALL(v)), v.end())
#define debug(x) cout << #x << ": " << x << endl
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define rep(i, n) FOR(i, 0, n)
#define RFOR(i, a, b) for (int i = (b - 1); i >= a; i--)
#define rrep(i, n) RFOR(i, 0, n)
#define INF INT_MAX
#define SUP INT_MIN
#define mins(a, b) a = min(a, b)
#define maxs(a, b) a = max(a, b)

// 4近傍
int dy[]={0, 1, 0, -1};
int dx[]={1, 0, -1, 0};

// 8近傍
// int dy[]={0,0,1,-1,1,1,-1,-1};
// int dx[]={1,-1,0,0,1,-1,1,-1};

// const ll MOD = 1000000007;

ll pow_mod(ll a, ll b, ll mod) {
    ll tmp = 1;
    a %= mod;
    if (b > 0) {
        tmp = pow_mod(a, b / 2, mod);
        if (b % 2)
            tmp = (((tmp * tmp) % mod) * a) % mod;
        else
            tmp = (tmp * tmp) % mod;
    }
    return tmp;
}
string s = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
void solve() {
    int n; cin >> n;
    vector<int> d;
    int size = s.size();
    rep(i,size) d.push_back(s[i] - '0');
    int val = 0;
    rrep(i,size){
        d[i] = d[i] * n + val;
        val = d[i] / 10;
        d[i] %= 10;
    }
    cout << val << ".";
    rep(i,size) cout << d[i];
    cout << endl;
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    solve();

    return 0;
}