#include <bits/stdc++.h>
using namespace std;

struct Point {
    long long  x, y;
    Point() {}
    Point(long long  _x, long long  _y) : x(_x), y(_y) {}
    bool operator<(Point &b) {
        return (this->x == b.x ? this->y < b.y : this->x < b.x);
    }
};

bool rightturn(Point pA, Point pB, Point pC) {
    return (long long)pA.x * (pB.y - pC.y) + pB.x * (pC.y - pA.y) + pC.x * (pA.y - pB.y) < 0;
}

bool leftturn(Point pA, Point pB, Point pC) {
    return (long long)pA.x * (pB.y - pC.y) + pB.x * (pC.y - pA.y) + pC.x * (pA.y - pB.y) > 0;
}

void ch(vector <Point> &in) {
    sort(in.begin(), in.end());
    Point first_point = in[0];
    Point second_point = in.back();
    vector <Point> convexhullup, convexhulldown;
    convexhullup.push_back(first_point);
    convexhulldown.push_back(first_point);
    for (long long  i = 1; i < in.size(); ++i) {
        if (i == in.size() - 1 || rightturn(first_point, in[i], second_point)) {
            while (convexhullup.size() >= 2 && !rightturn(convexhullup[convexhullup.size() - 2], convexhullup[convexhullup.size() - 1], in[i])) convexhullup.pop_back();
            convexhullup.push_back(in[i]);
        }
        if (i == in.size() - 1 || leftturn(first_point, in[i], second_point)) {
            while (convexhulldown.size() >= 2 && !leftturn(convexhulldown[convexhulldown.size() - 2], convexhulldown[convexhulldown.size() - 1], in[i])) convexhulldown.pop_back();
            convexhulldown.push_back(in[i]);
        }
    }
    in.clear();
    for (long long  i = 0; i < convexhullup.size(); ++i) in.push_back(convexhullup[i]);
    for (long long  i = convexhulldown.size() - 2; i > 0; --i) in.push_back(convexhulldown[i]);
}

int  main() {
    long long  a, b;
    int  n, l;
    cin >> n >> l;
    vector < Point > v;
    for (long long  i = 0; i < n; i++) {
        cin >> a >> b;
        v.push_back({a, b});
    }
    ch(v);
    double p = 0.0;
    for (int i = 0; i < v.size(); i++) {
        if (!i) {
            p += sqrtl((v[0].x - v.back().x) * (v[0].x - v.back().x) + (v[0].y - v.back().y) * (v[0].y - v.back().y));
        } else {
            p += sqrtl((v[i].x - v[i - 1].x) * (v[i].x - v[i - 1].x) + (v[i].y - v[i - 1].y) * (v[i].y - v[i - 1].y));
        }
    }
    p += 2 * acosl(-1) * l;
    cout << fixed << setprecision(12) << p;
}