#include <bits/stdc++.h>
using namespace std;
double n, k, tot, x[2], y[2];
int main() {
  cin >> n >> k;
  cin >> x[0] >> y[0];
  while (--n) {
    cin >> x[1] >> y[1];
    tot += sqrt((abs(x[1] - x[0]) * abs(x[1] - x[0])) +
                (abs(y[1] - y[0]) * abs(y[1] - y[0])));
    x[0] = x[1];
    y[0] = y[1];
  }
  tot *= k / 50;
  cout << setprecision(9) << tot << endl;
  return 0;
}
