#include <bits/stdc++.h>
using namespace std;
bool comp(pair<long long, long long> a, pair<long long, long long> b) {
  if (a.first == b.first) return a.second < b.second;
  return a.first < b.first;
}
long long binpow(long long a, long long b) {
  long long res = 1;
  while (b) {
    if (b & 1) res = res * a;
    a = a * a;
    b >>= 1;
  }
  return res;
}
bool isPrime(long long n) {
  for (long long i = 2; i < sqrt(n) + 1; i++) {
    if (n % i == 0) return 0;
  }
  return 1;
}
bool is_regular(string s, long long n) {
  long long x = 0;
  for (long long i = 0; i < n; i++) {
    x += (s[i] == '(' ? 1 : -1);
    if (x < 0) return false;
  }
  return !x ? true : false;
}
bool isP(string s) {
  long long i = 0, j = (long long)(s.size()) - 1;
  while (i < j) {
    if (s[i++] != s[j--]) return false;
  }
  return true;
}
long long sod(long long n) {
  long long sum = 0;
  while (n) {
    sum += n % 10;
    n /= 10;
  }
  return sum;
}
long long gcd(long long a, long long b) { return !b ? a : gcd(b, a % b); }
void add(vector<long long>& f, long long idx, long long val, long long n) {
  for (; idx < n; idx = idx + (idx & (-idx))) {
    f[idx] += val;
  }
}
long long point_query(vector<long long>& f, long long idx) {
  long long res = 0;
  for (; idx > 0; idx = idx - (idx & (-idx))) res += f[idx];
  return res;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long tt = 1, el = 1;
  while (tt--) {
    long long r, x, y, u, v;
    cin >> r >> x >> y >> u >> v;
    double d = sqrt(binpow(x - u, 2) + binpow(y - v, 2));
    long long res = ceil(d / (2 * r));
    cout << res;
  }
  return 0;
}
