#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using pii = pair<int, int>;
using vii = vector<pii>;
const int mod = 1e9 + 7;
const int inf = 1e9 + 100;
const ll inf64 = 1e18 + 100;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(20);
  double x, y, x2, y2, r;
  cin >> r >> x >> y >> x2 >> y2;
  int answer = ceil(sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2)) / (2 * r));
  cout << answer << "\n";
  return 0;
}
