#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:167772160")
using namespace std;
const double PI = 3.14159265358979323846;
const long long MODUL = 1000000007;
const long long MAXINT = 2e9 + 2;
const long long MAXLL = 2e18 + 2;
const double eps = 1e-8;
const int MAXN = 1e4 + 10;
long long x, y, xx, yy, d, r, ans;
void init() {
  cin >> r >> x >> y >> xx >> yy;
  r *= 2;
}
void solve() {
  d = (xx - x) * (xx - x) + (yy - y) * (yy - y);
  ans = sqrt(d / (r * r) * 1.0);
  if (ans * ans * r * r < d) ++ans;
}
void output() { cout << ans; }
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  init();
  solve();
  output();
  return 0;
}
