#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 9;
int main() {
  double r, x, y, xp, yp;
  cin >> r >> x >> y >> xp >> yp;
  double dist = sqrt((x - xp) * (x - xp) + (y - yp) * (y - yp));
  cerr << "dist"
       << ": " << dist << endl;
  ;
  double cont = 0, cant = r;
  while (cant < dist) {
    cont = cont + 1.0;
    cant = r * cont;
  }
  int asd = int(cont);
  cerr << "asd"
       << ": " << asd << endl;
  ;
  if (x == xp and y == yp)
    cout << 0;
  else if (dist < r)
    cout << 1;
  else {
    if (asd % 2 == 0)
      cout << asd / 2;
    else
      cout << (asd + 1) / 2;
  }
  return 0;
}
