#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  cout << ceil(double(d / (2 * r))) << "\n";
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
