#include <bits/stdc++.h>
using namespace std;
void solve() {
  int r, a, b, x, y;
  cin >> r >> a >> b >> x >> y;
  int s = 2 * r;
  float d = sqrt((a - x) * (a - x) + (b - y) * (b - y));
  int ans = floor(d) / s;
  if (floor(d) != ceil(d)) ans++;
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  t = 1;
  for (int i = 1; i <= t; i++) {
    solve();
  }
  return 0;
}
