#include <bits/stdc++.h>
using namespace std;
struct Point {
  int x, y;
  Point() {}
  Point(int a, int b) {
    x = a;
    y = b;
  }
};
double hypt(Point A, Point B) {
  return sqrt((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y));
}
int main() {
  int k, n;
  cin >> n >> k;
  vector<Point> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i].x >> v[i].y;
  }
  double ans = 0;
  for (int i = 1; i < n; i++) {
    ans += hypt(v[i], v[i - 1]);
  }
  ans *= k;
  ans /= 50;
  printf("%.10lf", ans);
  return 0;
}
