#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int x, y;
  cin >> x >> y;
  double d = 0;
  n--;
  while (n--) {
    int x1, y1;
    cin >> x1 >> y1;
    d += sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
    x = x1;
    y = y1;
  }
  printf("%f", (d * k) / 50);
}
