#include <bits/stdc++.h>
using namespace std;
int n, k, x[2005], y[2005];
double sum, d;
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (i > 0) {
      d = sqrt(pow(x[i] - x[i - 1], 2) + pow(y[i] - y[i - 1], 2));
      sum += d;
    }
  }
  sum = sum * k / 50;
  printf("%.9lf", sum);
}
