#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  double x, y, dis = 0;
  scanf("%lf %lf", &x, &y);
  complex<double> p = {x, y};
  for (int i = 1; i < n; i++) {
    scanf("%lf %lf", &x, &y);
    complex<double> q = {x, y};
    dis = dis + abs(p - q);
    p = q;
  }
  dis = (dis * (double)k) / (double)50;
  printf("%lf\n", dis);
  return 0;
}
