#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y, xx, yy;
  int n, k;
  double len = 0;
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    if (!i)
      cin >> xx >> yy;
    else {
      cin >> x >> y;
      len += sqrt((x - xx) * (x - xx) + (y - yy) * (y - yy));
      xx = x;
      yy = y;
    }
  }
  len = (len * k) / 50.0;
  printf("%.9lf", len);
  return 0;
}
