#include <bits/stdc++.h>
int main() {
  int x, y, xlast, ylast, n, k, i;
  double sum = 0.0f;
  scanf("%d%d", &n, &k);
  scanf("%d%d", &xlast, &ylast);
  for (i = 0; i < n - 1; i++) {
    scanf("%d%d", &x, &y);
    sum += sqrt(pow((double)x - xlast, 2) + pow((double)y - ylast, 2));
    xlast = x;
    ylast = y;
  }
  printf("%0.9lf", sum / 50 * k);
  return 0;
}
