#include <bits/stdc++.h>
int diru[] = {-1, -1, -1, 0, 0, 1, 1, 1};
int dirv[] = {-1, 0, 1, -1, 1, -1, 0, 1};
using namespace std;
template <class T>
T sq(T n) {
  return n * n;
}
template <class T>
T gcd(T a, T b) {
  return (b != 0 ? gcd<T>(b, a % b) : a);
}
template <class T>
T lcm(T a, T b) {
  return (a / gcd<T>(a, b) * b);
}
template <class T>
bool inside(T a, T b, T c) {
  return a <= b && b <= c;
}
template <class T>
void setmax(T &a, T b) {
  if (a < b) a = b;
}
template <class T>
void setmin(T &a, T b) {
  if (b < a) a = b;
}
template <class T>
T power(T N, T P) {
  return (P == 0) ? 1 : N * power(N, P - 1);
}
pair<int, int> in[110];
int main() {
  int n, T, t = 1, m, i, j, k;
  while (scanf("%d", &n) == 1) {
    scanf("%d", &k);
    double ans = 0;
    for (i = 0; i < n; i++) {
      scanf("%d", &in[i].first);
      scanf("%d", &in[i].second);
    }
    for (i = 1; i < n; i++) {
      ans += sqrt((double)((
          ((in[i].first - in[i - 1].first) * (in[i].first - in[i - 1].first)) +
          ((in[i].second - in[i - 1].second) *
           (in[i].second - in[i - 1].second)))));
    }
    ans /= (double)50.0;
    printf("%.15lf\n", ans * (double)k);
  }
  return 0;
}
