#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double dist = pow((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2), 0.5);
  int val = dist / (2 * r);
  if (dist - val * 2 * r == 0) {
    cout << val;
  } else {
    cout << val + 1;
  }
  return 0;
}
