#include <bits/stdc++.h>
using namespace std;
struct point {
  double x, y;
  point() {}
  point(double xx, double yy) {
    x = xx;
    y = yy;
  }
};
point p[50001];
double rs;
int n, k;
double Dist(point p1, point p2) {
  double dx, dy;
  dx = p1.x - p2.x;
  dy = p1.y - p2.y;
  return sqrt(dx * dx + dy * dy);
}
void Read_Input() {
  rs = 0.0;
  scanf("%d %d", &n, &k);
  scanf("%lf %lf", &p[1].x, &p[1].y);
  for (int i = 2; i <= n; i++) {
    scanf("%lf %lf", &p[i].x, &p[i].y);
    rs += Dist(p[i], p[i - 1]);
  }
  printf("%.9lf\n", (rs * (double)k) / 50);
}
int main() {
  Read_Input();
  return 0;
}
