#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  double dis;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  dis = sqrt(abs(x1 - x2) * abs(x1 - x2) + abs(y1 - y2) * abs(y1 - y2));
  int ans = dis / (r * 2);
  if (2 * r * ans != dis) ans++;
  cout << ans;
}
