#include <bits/stdc++.h>
using namespace std;
int n, k, xx, yy, x, y;
double ans;
double dist(int x, int y, int X, int Y) {
  return (sqrt((x - X) * (x - X) * 1.0 + (y - Y) * (y - Y)));
}
int main() {
  cin >> n >> k;
  scanf("%d%d", &xx, &yy);
  for (int i = 1; i < n; i++) {
    scanf("%d%d", &x, &y);
    ans += dist(xx, yy, x, y);
    xx = x;
    yy = y;
  }
  cout.setf(ios::fixed);
  cout.precision(20);
  cout << ans * k / 50;
}
