#include <bits/stdc++.h>
using namespace std;
float dl(int x1, int y1, int x2, int y2) {
  float s = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
  float d = sqrt(s);
  return d;
}
int main() {
  int n, k, x1, y1, x2, y2;
  float t, dd;
  cin >> n >> k;
  cin >> x1 >> y1;
  dd = 0;
  for (int i = 0; i < n; i++) {
    cin >> x2 >> y2;
    dd += dl(x1, y1, x2, y2);
    x1 = x2;
    y1 = y2;
  }
  t = dd / 50 * k;
  printf("%.10f", t);
  return 0;
}
