#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, x[101], y[101], i;
  float sum = 0;
  cin >> n >> k;
  cin >> x[0] >> y[0];
  for (i = 1; i < n; i++) {
    cin >> x[i] >> y[i];
    sum += sqrt((x[i] - x[i - 1]) * (x[i] - x[i - 1]) +
                (y[i] - y[i - 1]) * (y[i] - y[i - 1]));
  }
  float time;
  time = sum / 50.0 * k;
  cout.precision(8);
  cout << time << endl;
}
