#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, n, x, y;
  long double s = 0, s1;
  vector<int> vint1, vint2;
  cin >> k >> n;
  for (int i = 0; i < k; i++) {
    cin >> x >> y;
    vint1.push_back(x);
    vint2.push_back(y);
  }
  for (int i = 0; i < vint1.size() - 1; i++) {
    s1 = (((vint1[i + 1] - vint1[i]) * (vint1[i + 1] - vint1[i])) +
          ((vint2[i + 1] - vint2[i]) * (vint2[i + 1] - vint2[i])));
    s += sqrt(s1);
  }
  printf("%f", (s / 50) * n);
  cin >> n;
  return 0;
}
