#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, K;
  cin >> N >> K;
  int x, y;
  cin >> x >> y;
  double dist = 0;
  for (int i = 1; i < N; i++) {
    int x1, y1;
    cin >> x1 >> y1;
    dist += sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
    x = x1, y = y1;
  }
  printf("%.10f\n", dist / 50 * K);
  return 0;
}
