#include <bits/stdc++.h>
using namespace std;
double distance(int x1, int y1, int x2, int y2) {
  return sqrt(((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)));
}
int main() {
  int n, k;
  cin >> n >> k;
  double dist;
  for (int i = 0; i < n; i++) {
    int a, b, prevx, prevy;
    cin >> a >> b;
    if (i != 0) {
      dist += distance(a, b, prevx, prevy);
    }
    prevx = a;
    prevy = b;
  }
  double ans = (k * dist) / 50;
  printf("%.9lf", ans);
}
