#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x, y, i, x1, y1;
  double d;
  cin >> x >> y;
  for (i = 1; i < n; i++) {
    cin >> x1 >> y1;
    d = d + sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
    x = x1;
    y = y1;
  }
  double t = d / (double)50;
  t = t * k;
  printf("%.9lf\n", t);
  return 0;
}
