#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, K;
  cin >> N >> K;
  double res = 0;
  long double t1x, t1y, t2x, t2y;
  cin >> t1x >> t1y;
  for (int i = 1; i < N; ++i) {
    t2x = t1x;
    t2y = t1y;
    cin >> t1x >> t1y;
    res += sqrt((t1x - t2x) * (t1x - t2x) + (t1y - t2y) * (t1y - t2y));
  }
  printf("%.15lf\n", res * K / 50);
  return 0;
}
