#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int tc, n, a[N];
double mul(double x, double y) { return (x - y) * (x - y); }
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0);
  double r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double dis = mul(x1, x2) + mul(y2, y1);
  dis = sqrt(dis);
  int Ans = ceil(dis / (2 * r));
  cout << Ans << "\n";
  return 0;
}
