#include <bits/stdc++.h>
using namespace std;
void solve();
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
    cout << "\n";
  }
  cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
  return 0;
}
void solve() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int ans = ceil(sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y)) / (2.000 * r));
  cout << ans << "\n";
  return;
}
