#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  cin >> n >> k;
  double x1, y1, x2, y2, sum = 0;
  cin >> x1 >> y1;
  n -= 1;
  while (n--) {
    cin >> x2 >> y2;
    sum += sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
    x1 = x2;
    y1 = y2;
  }
  sum = (sum * k) / 50;
  printf("%.9f", sum);
  return 0;
}
