#include <bits/stdc++.h>
double dist(int x1, int y1, int x2, int y2) {
  return sqrt(pow(x1 - x2, 2.0) + pow(y1 - y2, 2.0));
}
int main(void) {
  int n, k, lx, ly, x, y;
  scanf("%d %d", &n, &k);
  scanf("%d %d", &lx, &ly);
  double total = 0;
  for (int i = 1; i < n; i++) {
    scanf("%d %d", &x, &y);
    total += dist(x, y, lx, ly);
    lx = x;
    ly = y;
  }
  total *= k;
  total /= 50;
  printf("%0.8f", total);
  return 0;
}
