#include <bits/stdc++.h>
using namespace std;
int r, a, b, c, d, x, y, sol, dist;
double di;
int main() {
  cin >> r >> a >> b >> c >> d;
  di = sqrt((a - c) * (a - c) + (b - d) * (b - d));
  dist = int(di);
  if (dist * 1.0 < di) dist++;
  r += r;
  sol = dist / r;
  if (dist % r) sol++;
  cout << sol;
  return 0;
}
