#include <bits/stdc++.h>
using namespace std;
const double EPS = 1E-9;
struct pt {
  double x, y;
  bool operator<(const pt& p) const {
    return x < p.x - EPS || abs(x - p.x) < EPS && y < p.y - EPS;
  }
};
int main() {
  pt n, k;
  int r;
  cin >> r >> n.x >> n.y >> k.x >> k.y;
  double d = 2 * r;
  double rast = sqrt((n.x - k.x) * (n.x - k.x) + (k.y - n.y) * (k.y - n.y));
  int k1 = (int)rast / d;
  int ans = 0;
  if (rast < 0.00001) {
    cout << 0;
    return 0;
  }
  double nec = rast - (int)rast;
  ans = (int)rast / d;
  if (nec > 0.00001 || ans * d < rast) {
    cout << ans + 1;
    return 0;
  }
  cout << ans;
}
