#include <bits/stdc++.h>
using namespace std;
struct point {
  double x;
  double y;
};
double distanc(point a, point b) {
  return sqrt(((a.x - b.x) * (a.x - b.x)) + ((a.y - b.y) * (a.y - b.y)));
}
int main() {
  int n;
  double k;
  cin >> n >> k;
  point p[n + 1];
  for (int i = 1; i <= n; i++) {
    cin >> p[i].x >> p[i].y;
  }
  double dis = 0;
  for (int i = 2; i <= n; i++) {
    dis = dis + distanc(p[i], p[i - 1]);
  }
  printf("%.9lf", dis * k / 50);
}
