#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  int g = (xx - x) * (xx - x);
  int e = (yy - y) * (yy - y);
  int ans;
  double a = ceil(sqrt(e + g));
  ans = ceil(a / (r * 2));
  cout << ans;
  return 0;
}
