#include <bits/stdc++.h>
using namespace std;
struct koor {
  int x, y;
};
int r;
int okr(double o) {
  if ((int)o == o)
    return (int)o;
  else
    return (int)o + 1;
}
int main() {
  koor a, b;
  cin >> r >> a.x >> a.y >> b.x >> b.y;
  int rast = okr(sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y)));
  if (rast % (2 * r) == 0)
    cout << rast / (4 * r * r);
  else
    cout << rast / (2 * r) + 1;
}
