#include <bits/stdc++.h>
struct point {
  double x;
  double y;
} p[102];
using namespace std;
int main() {
  int i = 0, n;
  double k, d = 0;
  scanf("%d%lf", &n, &k);
  while (i < n) {
    scanf("%lf%lf", &p[i].x, &p[i].y);
    if (i > 0) {
      d += sqrt((p[i].x - p[i - 1].x) * (p[i].x - p[i - 1].x) +
                (p[i].y - p[i - 1].y) * (p[i].y - p[i - 1].y));
    }
    i++;
  }
  d /= 50;
  printf("%.9lf\n", k * d);
  return 0;
}
