#include <bits/stdc++.h>
using namespace std;
const int eps = 1e6 + 5;
const double pi = acos(-1.0);
struct s {
  double x, y;
} pre[105];
int main() {
  int n, k;
  while (~scanf("%d%d", &n, &k)) {
    for (int i = 0; i < n; i++) {
      scanf("%lf%lf", &pre[i].x, &pre[i].y);
    }
    double ans = 0;
    for (int i = 0; i < n - 1; i++) {
      ans += sqrt((pre[i + 1].x - pre[i].x) * (pre[i + 1].x - pre[i].x) +
                  (pre[i + 1].y - pre[i].y) * (pre[i + 1].y - pre[i].y));
    }
    ans *= k;
    printf("%.9f\n", ans / 50);
  }
  return 0;
}
