#include <bits/stdc++.h>
using namespace std;
long long int ar[500009], br[500009];
int main() {
  long long int n, i;
  double a, b, c = 0.0, j, k, x, y, z;
  cin >> n >> k;
  cout << fixed << setprecision(12);
  cin >> j >> z;
  for (i = 2; i <= n; i++) {
    cin >> a >> b;
    x = sqrt(((a - j) * (a - j)) + ((b - z) * (b - z)));
    c += x;
    j = a;
    z = b;
  }
  cout << ((c * k) / 50.0) << endl;
}
