#include <bits/stdc++.h>
using namespace std;
double r, x, y, x2, y2;
int ans = 0;
void run() {
  cin >> r >> x >> y >> x2 >> y2;
  double d = (x2 - x) * (x2 - x) + (y2 - y) * (y2 - y);
  d = sqrt(d);
  ans += (int)floor(d / (2 * r));
  d -= ans * (2 * r);
  if (d > 0) ans++;
  cout << ans << endl;
}
int main() {
  run();
  return 0;
}
