#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x, y, a, b;
  double dis = 0;
  cin >> x >> y;
  a = x;
  b = y;
  n--;
  while (n--) {
    cin >> x >> y;
    dis += (double)sqrt(pow(y - b, 2) + pow(x - a, 2));
    a = x;
    b = y;
  }
  dis = (dis / 50) * k;
  printf("%.6f", dis);
  return 0;
}
