#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  double d;
  d = sqrt(pow((a - x), 2) + pow((b - y), 2));
  d = abs(d - r);
  cout << (int)((d + r - 1) / r) << endl;
  return 0;
}
