#include <bits/stdc++.h>
using namespace std;
double n, k, ans;
pair<double, double> coor[1000];
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> coor[i].first >> coor[i].second;
  for (int i = 1; i < n; i++)
    ans += sqrt((coor[i].first - coor[i - 1].first) *
                    (coor[i].first - coor[i - 1].first) +
                (coor[i].second - coor[i - 1].second) *
                    (coor[i].second - coor[i - 1].second));
  printf("%.9f", (ans * k) / 50);
}
