#include <bits/stdc++.h>
using namespace std;
int mod = 1e9 + 7, gaymod = 998244353, MAX = 1000000000, pomod = 1073741824;
int gcd(int x, int y) {
  if (y == 0) return x;
  return gcd(y, x % y);
}
long long lcm(long long a, long long b) {
  long long g = gcd(a, b);
  return a / g * b;
}
long long binexp(long long a, long long b) {
  if (b == 0) return 1;
  long long res = binexp(a, b / 2);
  if (b % 2)
    return ((res % mod) * (res % mod) * (a % mod));
  else
    return ((res % mod) * (res % mod));
}
int prime(long long x) {
  if (x % 2 == 0 && x != 2)
    return 0;
  else {
    for (int i = 3; long long(i * i) <= x; i += 2) {
      if (x % i == 0) return 0;
    }
  }
  return 1;
}
const int N = 2e+5;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  mt19937 rng(
      (unsigned int)chrono::steady_clock::now().time_since_epoch().count());
  ;
  int t = 1;
  while (t--) {
    int r, x, y, x1, y1;
    cin >> r >> x >> y >> x1 >> y1;
    double dis;
    dis = (x - x1) * (x - x1) + (y - y1) * (y - y1);
    dis = sqrt(dis);
    int ans = 0;
    while (dis > 2 * r) {
      ans++;
      dis -= 2 * r;
    }
    if (dis != 0) ans++;
    cout << ans;
    cout << "\n";
  }
  return 0;
}
