#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double a[4], sum = 0;
  cin >> a[0] >> a[1];
  n--;
  while (n--) {
    scanf("%lf %lf", a + 2, a + 3);
    sum += sqrt((a[2] - a[0]) * (a[2] - a[0]) + (a[3] - a[1]) * (a[3] - a[1]));
    a[0] = a[2];
    a[1] = a[3];
  }
  printf("%0.9lf\n", (sum / 50.0) * k);
  return 0;
}
