#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x0, y0, x1, y1;
  double l;
  scanf("%lf%lf%lf%lf%lf", &r, &x0, &y0, &x1, &y1);
  l = sqrt((x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1));
  int k;
  k = (int)(l / 2 / r);
  if (l - double(k) * r * 2 > 0) k++;
  cout << k << endl;
}
