#include <bits/stdc++.h>
struct point {
  int x, y;
};
double dis(point a, point b) {
  double ans;
  ans = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
  return ans;
}
int main() {
  int n, k;
  double sum;
  scanf("%d%d", &n, &k);
  sum = 0;
  struct point t1, t2;
  for (int i = 1; i <= n; i++) {
    int tx, ty;
    scanf("%d%d", &tx, &ty);
    t1.x = t2.x;
    t1.y = t2.y;
    t2.x = tx;
    t2.y = ty;
    if (i != 1) {
      sum += dis(t1, t2);
    }
  }
  printf("%lf\n", sum * k / 50);
  return 0;
}
