#include <bits/stdc++.h>
using namespace std;
double dist(double a, double b, double c, double d) {
  double res = ((a - c) * (a - c));
  res += ((b - d) * (b - d));
  res = sqrt(res);
  return res;
}
int main() {
  int n;
  double k;
  double res = 0;
  cin >> n >> k;
  double a, b, c, d;
  for (int i = 0; i < n; i++) {
    if (i == 0) {
      cin >> a >> b;
      continue;
    }
    c = a;
    d = b;
    cin >> a >> b;
    res += dist(a, b, c, d);
  }
  res /= 50.0;
  res *= k;
  printf("%.9f\n", res);
  return 0;
}
