#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double dist = 0;
  int prevx, prevy;
  cin >> prevx >> prevy;
  for (int i = 1; i < n; i++) {
    int x, y;
    cin >> x >> y;
    dist += sqrt((x - prevx) * (x - prevx) + (y - prevy) * (y - prevy));
    prevx = x;
    prevy = y;
  }
  cout << fixed << setprecision(9) << abs((dist / 50.0) * k);
}
