#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, a, b, i, c, d;
  double total;
  scanf("%d %d", &n, &k);
  scanf("%d %d", &a, &b);
  total = 0;
  for (i = 0; i < n - 1; i++) {
    scanf("%d %d", &c, &d);
    total = total + sqrt(((c - a) * (c - a)) + ((d - b) * (d - b)));
    a = c;
    b = d;
  }
  total = (total * k) / 50;
  printf("%lf\n", total);
  getchar();
  return 0;
}
