#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
const int N = 1e2 + 5, M = 100 + 5, OO = 0x3f3f3f3f, mod = 1e9 + 7, base = 131,
          mod2 = 1000136437, mod3 = 998244353;
const double EPS = 1e-9;
int n, k;
complex<double> tmp;
long double ans;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    complex<double> p(a, b);
    if (i) {
      ans += hypot(p.real() - tmp.real(), p.imag() - tmp.imag());
    }
    tmp = p;
  }
  cout << fixed << setprecision(6) << ans * (k * 1.0 / 50.0);
  return 0;
}
