#include <bits/stdc++.h>
using namespace std;
void solve() {
  int r, x_1, y_1, x_2, y_2;
  cin >> r >> x_1 >> y_1 >> x_2 >> y_2;
  double distance =
      sqrtl((x_1 - x_2) * (x_1 - x_2) + (y_1 - y_2) * (y_1 - y_2));
  distance = distance / (2 * r);
  cout << ceill(distance) << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  while (t--) solve();
}
