1020

// OK TIMUS 1020

# include <iostream>
# include <cmath>
# include <vector>
# include <iomanip>
using namespace std;
double distance(pair<double, double> f, pair<double, double> s) {
    double x1 = f.first;
    double y1 = f.second;
    double x2 = s.first;
    double y2 = s.second;
    double dis_x = x1 - x2;
    double dis_y = y1 - y2;
    return sqrt(dis_x * dis_x + dis_y * dis_y);
}

const double PI = 3.1415926535;
int main() {
    double r;
    size_t n;
    double sum = 0;
    cin >> n >> r;
    double res = 2 * PI * r;
    vector<pair<double, double>> m(n);
    for (size_t i = 0; i < n; i++) {
        cin >> m[i].first >> m[i].second;
    }
    for (size_t i = 0; i < n; i++) {
        size_t prev = n - 1;
        if (i != 0) {
            prev = i - 1;
        }
        sum += distance(m[i], m[prev]);
    }
    res += sum;
    cout << fixed << setprecision(2) << res;
    return 0;
}