#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e2 + 5;
struct Point {
  double X, Y;
  void Input() { scanf("%lf%lf", &X, &Y); }
  Point operator-(const Point &B) const { return Point{X - B.X, Y - B.Y}; }
  double operator*(const Point &B) const { return X * B.X + Y * B.Y; }
  double operator^(const Point &B) const { return X * B.Y - Y * B.X; }
};
double Distance(Point A, Point B) { return sqrt((B - A) * (B - A)); }
int N, K;
double Ans;
Point points[maxn];
int main(int argc, char *argv[]) {
  scanf("%d%d", &N, &K);
  Ans = 0.0;
  points[0].Input();
  for (int i = 1; i < N; ++i) {
    points[i].Input();
    Ans += Distance(points[i], points[i - 1]);
  }
  printf("%.9lf\n", Ans * K / 50.0);
  return 0;
}
