#include <bits/stdc++.h>
using namespace std;
int x[1000], y[1000];
double sqr(double x) { return x * x; }
int main() {
  int i, j, k, n;
  double an = 0;
  scanf("%d%d", &n, &k);
  for (i = 0; i < n; i++) scanf("%d%d", &x[i], &y[i]);
  for (i = 1; i < n; i++)
    an += sqrt(sqr(x[i] - x[i - 1]) + sqr(y[i] - y[i - 1]));
  printf("%.10lf\n", an * k / 50);
  return 0;
}
