#include<cmath>
#include<iostream>

int main(){
    double r; std::cin >> r;
    std::cout << 2*M_PI*r << std::endl;
    return 0;
}
#include <iostream>
#include <cmath>
#include <vector>
#include <map>
#include <iomanip>
#include <algorithm>
#include <sstream>
#include <string>
#include <math.h>
#include <set>
#include <deque>
#include <queue>
using namespace std;
typedef long long ll;
const int mod = 1000000007;

int main() {
    ios::sync_with_stdio(false);
    string s;
    cin >> s;
    cout << 2018;
    for (int i = 4 ; i < s.length() ; i++) cout << s[i];
}