#include <bits/stdc++.h>
using std::cin;
using std::cout;
using std::endl;
using std::min;
using std::sort;
using std::sqrt;
using std::stack;
using std::string;
using std::vector;
int main() {
  int n, k;
  cin >> n >> k;
  double s = 0, x, y, x0, y0;
  cin >> x0 >> y0;
  for (int i = 1; i < n; ++i) {
    cin >> x >> y;
    s += sqrt((x - x0) * (x - x0) + (y - y0) * (y - y0));
    x0 = x;
    y0 = y;
  }
  s = s * k / 50;
  printf("%lf\n", s);
  return 0;
}
