#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repe(i, n) for (int i = 0; i <= (n); ++i)
#define all(x) (x).begin(),(x).end()
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
typedef long long ll;
const int INF = 1e9;
const ll mod = 1000000007;
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a*b / gcd(a,b);}

int main() {
    string s;
    cin >> s;
    if (s.size() < 3) {
        cout << s << "\n";
    } else {
        cout << s[2] << s[1] << s[0] << "\n";
    }
}

#include <iostream>
#include <math.h>

using namespace std;
void Solve(int a)
{
	const double pi = 3.14;
	float ans;
	ans = 2 * pi * a;
	cout << ans;
}
int main()
{
	int x;
	cin >> x;
	Solve(x);
	return 0;
}