#include <bits/stdc++.h>
int main() {
  int n, k, a[100], b[100], i;
  double s = 0;
  scanf("%d", &(n)), scanf("%d", &(k));
  for (i = 0; i < n; i++) scanf("%d", &(a[i])), scanf("%d", &(b[i]));
  for (i = 1; i < n; i++)
    s += sqrt((a[i] - a[i - 1]) * (a[i] - a[i - 1]) +
              (b[i] - b[i - 1]) * (b[i] - b[i - 1]));
  s *= k;
  printf("%.9f\n", s / 50);
  return 0;
}
