#include <bits/stdc++.h>
using namespace std;
int64_t gcd(int64_t a, int64_t b) { return (b == 0 ? a : gcd(b, a % b)); }
int64_t rnd(int64_t ans, int64_t res) {
  while (ans * ans < res) ans++;
  while (ans > 0 && (ans - 1) * (ans - 1) >= res) ans--;
  return ans;
}
void solve() {
  int64_t r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  int64_t d = (xx - x) * (xx - x) + (yy - y) * (yy - y);
  d -= 1e-12;
  r *= 2;
  cout << ceil(d / r) << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false), cin.tie(nullptr);
  ;
  int64_t tests = 1;
  while (tests-- > 0) solve();
  return 0;
}
