#include <bits/stdc++.h>
const long long int N = 1e9 + 7;
const long long int mod = 1e9 + 7;
using namespace std;
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second < b.second);
}
bool prime(long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (long long int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
bool isPowerOfTwo(long long int n) {
  if (n == 0) return false;
  return (ceil(log2(n)) == floor(log2(n)));
}
void SieveOfEratosthenes(long long int n) {
  bool prime[n + 1];
  memset(prime, true, sizeof(prime));
  for (long long int p = 2; p * p <= n; p++) {
    if (prime[p] == true) {
      for (long long int i = p * p; i <= n; i += p) prime[i] = false;
    }
  }
  for (long long int p = 2; p <= n; p++)
    if (prime[p]) cout << p << " ";
}
long long int modularinv(long long int x, long long int n) {
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
    return modularinv((x * x) % mod, n / 2);
  else
    return (x * modularinv((x * x) % mod, (n - 1) / 2)) % mod;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
map<long long int, long long int> mpp;
void primeFactors(long long int n) {
  while (n % 2 == 0) {
    mpp[2]++;
    n = n / 2;
  }
  for (int i = 3; i <= sqrt(n); i = i + 2) {
    while (n % i == 0) {
      mpp[i]++;
      n = n / i;
    }
  }
  if (n > 2) mpp[n]++;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long int t, i, p, q, f, h, c, m, j, k, n, a, b, x, pos, r;
  t = 1;
  while (t--) {
    cin >> r >> a >> b >> p >> q;
    long long int d = 2 * r;
    double g = sqrt(pow(abs(p - a), 2) + pow(abs(q - b), 2));
    long long int f = g / d;
    g -= f * d;
    if (g != 0) f++;
    cout << f << '\n';
  }
}
