#include <bits/stdc++.h>
using namespace std;
struct point {
  double x, y;
} points[100000];
double dis(point a, point b) {
  double dx = a.x - b.x;
  double dy = a.y - b.y;
  return sqrt(dx * dx + dy * dy);
}
int main() {
  int n;
  double k;
  while (scanf("%d%lf", &n, &k) != EOF) {
    double ans = 0;
    for (int i = 0; i < n; i++) {
      scanf("%lf%lf", &points[i].x, &points[i].y);
    }
    for (int i = 0; i + 1 < n; i++) {
      ans += dis(points[i], points[i + 1]);
    }
    ans = ans * k;
    printf("%.9f\n", ans / 50.0);
  }
}
