#include <bits/stdc++.h>
using namespace std;
float dist(float x1, float y1, float x2, float y2) {
  float d = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
  return d;
}
int main() {
  int n, k;
  cin >> n >> k;
  float x1, y1;
  float x2, y2;
  float sum = 0;
  cin >> x1 >> y1;
  for (int a = 1; a < n; a++) {
    cin >> x2 >> y2;
    sum += dist(x1, y1, x2, y2);
    x1 = x2;
    y1 = y2;
  }
  float ans = sum / (float)50;
  ans = ans * (float)k;
  printf("%f\n", ans);
  return 0;
}
