#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  double x, y, x1, y1;
  scanf("%lf %lf", &x, &y);
  double l = 0;
  for (int i = 1; i < n; i++) {
    scanf("%lf %lf", &x1, &y1);
    l += sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
    x = x1;
    y = y1;
  }
  l *= k;
  l /= 50;
  printf("%.10lf\n", l);
  return 0;
}
