#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

string sum(string a, string b) {
	if (a.size() > b.size()) swap(a, b);
	
	reverse(a.begin(), a.end());
	reverse(b.begin(), b.end());
	
	string res = "";
	int c = 0;
	REP(i, a.size()) {
		c += a[i] - '0' + b[i] - '0';
		res.push_back(c % 10 + '0');
		c /= 10;
	}
	FOR(i, a.size(), b.size()) {
		c += b[i] - '0';
		res.push_back(c % 10 + '0');
		c /= 10;
	}
	if (c > 0) res.push_back(c + '0');
	
	reverse(res.begin(), res.end());
	
	return res;
}

string product(string a, string b) {
	if (a == "0" || b == "0") return "0";
	
	reverse(a.begin(), a.end());
	reverse(b.begin(), b.end());
	
	string res = "0";
	REP(i, a.size()) {
		string plus = "";
		int c = 0;
		REP(j, b.size()) {
			c += (a[i] - '0') * (b[j] - '0');
			plus.push_back(c % 10 + '0');
			c /= 10;
		}
		if (c > 0) plus.push_back(c % 10 + '0');
		reverse(plus.begin(), plus.end());
		REP(j, i) plus.push_back('0');
		res = sum(res, plus);
	}
	
	return res;
}

string D = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";

int main() {
	string n;
	cin >> n;
	
	string ans = product(D, n);
	
	if (D.size() == ans.size()) ans.insert(0, "0.");
	else ans.insert(ans.size() - D.size(), ".");
	
	cout << ans << endl;
	
	return 0;
}