#include <bits/stdc++.h>
using namespace std;
const int64_t MAXN = 1000000007;
struct point {
  int64_t x = 0;
  int64_t y = 0;
  point(const int64_t& x, const int64_t& y) : x(x), y(y) {}
  static point read() {
    int64_t x, y;
    cin >> x >> y;
    return point(x, y);
  }
};
double distance(const int64_t& x1, const int64_t& y1, const int64_t& x2,
                const int64_t& y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
signed main() {
  int64_t n, k;
  cin >> n >> k;
  double total = 0.0;
  int64_t x1, y1;
  int64_t x2, y2;
  cin >> x1 >> y1;
  while (--n) {
    cin >> x2 >> y2;
    total += distance(x1, y1, x2, y2);
    x1 = x2;
    y1 = y2;
  }
  total = total * k / 50;
  printf("%.6f", total);
  return 0;
}
