#include <bits/stdc++.h>
using namespace std;
const int INF = 1 << 30;
int main() {
  int n, k;
  cin >> n >> k;
  long double sum = 0.;
  long double lx, ly, x, y;
  cin >> lx >> ly;
  for (int i = 1; i < n; ++i) {
    cin >> x >> y;
    sum += sqrt((lx - x) * (lx - x) + (ly - y) * (ly - y));
    swap(x, lx), swap(y, ly);
  }
  cout.precision(8);
  cout.setf(ios::fixed);
  cout << k * sum / 50.;
  return 0;
}
