#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x, y, lastX, lastY;
  double ans = 0;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    if (i > 0) {
      int dx = (x - lastX);
      int dy = (y - lastY);
      ans += sqrt(double(dx * dx + dy * dy));
    }
    lastX = x;
    lastY = y;
  }
  double z = 0;
  if (ans == 0)
    printf("%0.9f\n", z);
  else
    printf("%0.9f\n", k * ans / 50);
  return 0;
}
