#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
const char nl = '\n';
long long gcd(long long a, long long b) {
  if (b != 0) return gcd(b, a % b);
  return a;
}
template <typename T>
vector<vector<T>> split(vector<T> s, T t) {
  int n = s.size();
  vector<vector<T>> ans;
  vector<T> x;
  for (int i = 0; i < n; ++i) {
    if (s[i] != t)
      x += s[i];
    else {
      ans.push_back(x);
      x.clear();
    }
  }
  ans.push_back(x);
  return ans;
}
struct segtree {
  vector<long long> tree;
  int size;
  void init(int n) {
    size = 1;
    while (size < n) size *= 2;
    tree.assign(2 * size - 1, 0);
  }
  void set(int i, int v, int x, int lx, int rx) {
    if (rx - lx == 1) {
      tree[x] = v;
      return;
    }
    int m = (lx + rx) / 2;
    if (i < m) {
      set(i, v, 2 * x + 1, lx, m);
    } else {
      set(i, v, 2 * x + 2, m, rx);
    }
    tree[x] = tree[2 * x + 1] + tree[2 * x + 2];
  }
  void set(int i, int v) { set(i, v, 0, 0, size); }
  long long s(int l, int r, int x, int lx, int rx) {
    if (l >= rx || lx >= r) {
      return 0;
    }
    if (lx >= l && rx <= r) {
      return tree[x];
    }
    int m = (lx + rx) / 2;
    long long s1 = s(l, r, 2 * x + 1, lx, m);
    long long s2 = s(l, r, 2 * x + 2, m, rx);
    return s1 + s2;
  }
  long long s(int l, int r) { return s(l, r, 0, 0, size); }
};
int get(int x, vector<int>& p) { return p[x]; }
void un(int x, int y, vector<int>& p, vector<set<int>>& g) {
  x = p[x];
  y = p[y];
  if (x != y) {
    if (g[x].size() > g[y].size()) swap(x, y);
    for (auto& i : g[x]) {
      p[i] = y;
      g[y].insert(i);
    }
    g[x].clear();
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double r, x, y, xs, ys;
  cin >> r >> x >> y >> xs >> ys;
  cout << ceil(sqrt((xs - x) * (xs - x) + (ys - y) * (ys - y)) / (2 * r));
  return 0;
}
