#include <bits/stdc++.h>
using namespace std;
struct point {
  int x, y;
};
long double dif(point p1, point p2) {
  return sqrt(pow(p1.x - p2.x, 2) + pow(p1.y - p2.y, 2));
}
int main() {
  int n, k;
  long double sum = 0;
  point p1, p2;
  cin >> n >> k;
  n--;
  cin >> p1.x >> p1.y;
  while (n--) {
    cin >> p2.x >> p2.y;
    sum += dif(p1, p2);
    p1 = p2;
  }
  cout << setprecision(7) << sum * k / 50;
  return 0;
}
