#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, x, y, xx, yy;
  cin >> n >> k;
  cin >> x >> y;
  long double ans = 0;
  for (int i = 1; i < n; i++) {
    cin >> xx >> yy;
    ans += sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
    x = xx;
    y = yy;
  }
  ans *= k;
  ans /= 50;
  cout.precision(10);
  cout << fixed << ans;
}
