#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  double lt = 0;
  double x0, y0;
  cin >> x0 >> y0;
  for (int q = 1; q < n; q++) {
    double x, y;
    cin >> x >> y;
    double a;
    a = sqrt((x - x0) * (x - x0) + (y - y0) * (y - y0));
    lt += a;
    x0 = x;
    y0 = y;
  }
  lt *= k;
  lt /= 50;
  printf("%0.8f", lt);
  return 0;
}
