#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, x[120], y[120];
  double res = 0;
  scanf("%d%d", &n, &k);
  for (int i = 0; i < n; i++) scanf("%d%d", &x[i], &y[i]);
  for (int i = 0; i < n - 1; i++)
    res += sqrtl(((x[i] - x[i + 1]) * (x[i] - x[i + 1])) +
                 ((y[i] - y[i + 1]) * (y[i] - y[i + 1])));
  printf("%.9lf", res * k / 50);
}
