#include <bits/stdc++.h>
using namespace std;
int n, k, x[105], y[105];
double s;
int main(void) {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
  int j = 1;
  while (j < n) {
    s += sqrt((double)(y[j] - y[j - 1]) * (y[j] - y[j - 1]) +
              (double)(x[j] - x[j - 1]) * (x[j] - x[j - 1]));
    j++;
  }
  printf("%0.7f", s * k * 0.02);
  return 0;
}
