#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double k;
  cin >> n >> k;
  int xPrev, yPrev;
  cin >> xPrev >> yPrev;
  double l = 0;
  for (int i = 1; i < n; i++) {
    double xCur, yCur;
    cin >> xCur >> yCur;
    l +=
        sqrt((xCur - xPrev) * (xCur - xPrev) + (yCur - yPrev) * (yCur - yPrev));
    xPrev = xCur;
    yPrev = yCur;
  }
  cout << setprecision(8) << fixed << k * l / 50;
  return 0;
}
