#include <bits/stdc++.h>
using namespace std;
double dist(int x1, int x2, int y1, int y2) {
  return sqrt(pow((x1 - x2), 2) + pow((y1 - y2), 2));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int n, k;
  cin >> n >> k;
  int a[n], b[n];
  for (long long int i = 0; i < n; i++) cin >> a[i] >> b[i];
  double ans = 0;
  for (long long int i = 0; i < n - 1; i++) {
    ans += dist(a[i], a[i + 1], b[i], b[i + 1]);
  }
  ans /= 50;
  ans = ans * k;
  printf("%.9f", ans);
  return 0;
}
