#include <bits/stdc++.h>
using namespace std;
int n, k;
double a[101], b[101], sum = 0;
double f(int i) {
  return sqrt((a[i] - a[i + 1]) * (a[i] - a[i + 1]) +
              (b[i] - b[i + 1]) * (b[i] - b[i + 1]));
}
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> a[i] >> b[i];
  for (int i = 0; i < n - 1; i++) {
    sum += f(i);
  }
  sum /= 50;
  sum *= k;
  printf("%.10lf", sum);
  return 0;
}
