#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) { return (b == 0 ? a : gcd(b, a % b)); }
void solve() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int xd = (x1 - x);
  int yd = (y1 - y);
  int64_t dist = xd * xd + yd * yd;
  cout << ceil(sqrt(dist) / (2 * r)) << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false), cin.tie(nullptr);
  ;
  int tests = 1;
  while (tests-- > 0) solve();
  return 0;
}
