#include <bits/stdc++.h>
using namespace std;
const long double EPS = 1E-9;
const int INF = (int)1E9;
const long long INF64 = (long long)1E18;
const long double PI = 2 * acos(.0);
double dist(long long x, long long y, long long px, long long py) {
  return sqrt(1.0 * ((x - px) * (x - px) + (y - py) * (y - py)));
}
int main() {
  long long n, k;
  double x, y, px, py;
  double segment = 0;
  cin >> n >> k;
  cin >> px >> py;
  for (int i = 0; i < (int)(n - 1); i++) {
    cin >> x >> y;
    segment += dist(x, y, px, py);
    px = x;
    py = y;
  }
  printf("%.9f\n", (k * segment / 50.0));
  return 0;
}
