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

template <typename T>
void chmin(T &x, const T &y) {
    if (x > y)
        x = y;
}
template <typename T>
void chmax(T &x, const T &y) {
    if (x < y)
        x = y;
}
typedef int64_t s64;
typedef uint64_t u64;
typedef uint32_t u32;
typedef pair<int, int> pii;
#define rep(i, l, r) for (int i = l; i <= r; ++i)
#define per(i, r, l) for (int i = r; i >= l; --i)
#define rep0(i, l, r) for (int i = l; i < r; ++i)
#define gc (c = getchar())
int read() {
    char c;
    while (gc < '-')
        ;
    if (c == '-') {
        int x = gc - '0';
        while (gc >= '0') x = x * 10 + c - '0';
        return -x;
    }
    int x = c - '0';
    while (gc >= '0') x = x * 10 + c - '0';
    return x;
}
#undef gc

const int N = 100 + 5;
const double PI = acos(-1);
struct Point {
    double x, y;
    void print() { printf("%.9f %.9f\n", x, y); }
    Point rotate(const double &a) { return { x * cos(a) - y * sin(a), y * cos(a) + x * sin(a) }; }
};
Point operator-(const Point &a, const Point &b) { return { a.x - b.x, a.y - b.y }; }
Point operator+(const Point &a, const Point &b) { return { a.x + b.x, a.y + b.y }; }
Point operator*(const Point &a, const double &k) { return { a.x * k, a.y * k }; }
double operator*(const Point &a, const Point &b) { return a.x * b.y - b.x * a.y; }
double sqr(const double &x) { return x * x; }
double dis(const Point &a, const Point &b) { return sqrt(sqr(a.x - b.x) + sqr(a.y - b.y)); }
double dis2(const Point &a, const Point &b) { return sqr(a.x - b.x) + sqr(a.y - b.y); }
Point rotate(const Point &p, const Point &O, const double &a) { return O + (p - O).rotate(a); }
Point p[N];
int n, r;
bool check(const Point &O) {
    rep(j, 1, n) if (dis2(p[j], O) > r * r + 1e-9) return 0;
    return 1;
}
Point work(int i, int r) {
    Point a = p[i], b = p[i + 1];
    Point mid = (a + b) * 0.5;
    double sqr_len = sqr(r) - (sqr(a.x - mid.x) + sqr(a.y - mid.y));
    Point d = b - a;
    swap(d.x, d.y);
    d.x *= -1;
    d = d * sqrt(sqr_len / (sqr(d.x) + sqr(d.y)));
    //  assert(fabs(sqr(d.x)+sqr(d.y)-sqr_len)<1e-9);
    Point c = mid + d;
    if (!check(c))
        return mid - d;
    return c;
}

int main() {
#ifdef kcz
    freopen("1.in", "r", stdin);  // freopen("1.out","w",stdout);
#endif
    cin >> n >> r;
    rep(i, 1, n) cin >> p[i].x >> p[i].y;
    double ans = 0;
    p[n + 1] = p[1];
    p[0] = p[n];
    Point O = work(1, r);
    O.print();
    rep(i, 2, n) {
        double l = 0, r = PI;
        rep(tmp, 1, 100) {
            double mid = (l + r) / 2;
            if (check(rotate(O, p[i], mid)))
                l = mid;
            else
                r = mid;
        }
        //  printf("%.9f\n",l/2/PI*360);
        O = rotate(O, p[i], l);
        //  printf("%.9f %.9f\n",dis(O,p[i+1]),dis(O,p[i]));
        //  O.print();
        ans += fabs(l) * dis(p[i], p[1]);
        // printf("%.9f\n",dis(p[i],p[1]));
    }
    printf("%.9f\n", ans);
}