#include <bits/stdc++.h>
using namespace std;
int x[1000], y[1000];
int main() {
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  double d = 0;
  for (int i = 0; i + 1 < n; i++) {
    d += sqrt((x[i] - x[i + 1]) * (x[i] - x[i + 1]) +
              (y[i] - y[i + 1]) * (y[i] - y[i + 1]));
  }
  d = d / (double)50;
  d = d * k;
  printf("%.10lf", d);
}
