#include <bits/stdc++.h>
struct Point {
  int x, y;
};
double dist(Point p1, Point p2) {
  return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
}
int main(void) {
  int n, k, i;
  double s = 0.0;
  scanf("%d %d", &n, &k);
  Point p1, p2;
  scanf("%d %d", &p1.x, &p1.y);
  for (i = 1; i < n; i++) {
    scanf("%d %d", &p2.x, &p2.y);
    s += dist(p1, p2);
    p1 = p2;
  }
  s = s * k / 50;
  printf("%.10f", s);
  return 0;
}
