#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double a, b;
  cin >> a >> b;
  double a1, b1;
  a1 = a;
  b1 = b;
  n--;
  double ans = 0;
  while (n--) {
    cin >> a >> b;
    ans += sqrt(pow(a1 - a, 2) + pow(b1 - b, 2));
    a1 = a, b1 = b;
  }
  printf("%.9lf", ans / 50 * k);
}
