#include <bits/stdc++.h>
using namespace std;
int n, k, a[109], b[109];
long double tmp, ans;
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> a[i] >> b[i];
  }
  for (int i = 1; i < n; i++) {
    tmp = sqrt(((a[i] - a[i - 1]) * (a[i] - a[i - 1])) +
               ((b[i] - b[i - 1]) * (b[i] - b[i - 1])));
    ans += tmp;
  }
  ans /= 50;
  ans *= k;
  cout << fixed << setprecision(6) << ans << endl;
  return 0;
}
