#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double length = 0.0;
  int x;
  int y;
  for (int i = 0; i < n; ++i) {
    int tx, ty;
    cin >> tx >> ty;
    if (i) length += sqrt((tx - x) * (tx - x) + (ty - y) * (ty - y)) / 50.0;
    x = tx;
    y = ty;
  }
  cout << setprecision(15) << k * length << endl;
  return 0;
}
