#include <bits/stdc++.h>
using namespace std;
vector<string> vec_splitter(string s) {
  s += ',';
  vector<string> res;
  while (!s.empty()) {
    res.push_back(s.substr(0, s.find(',')));
    s = s.substr(s.find(',') + 1);
  }
  return res;
}
void debug_out(vector<string> __attribute__((unused)) args,
               __attribute__((unused)) int idx,
               __attribute__((unused)) int LINE_NUM) {
  cerr << endl;
}
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
  if (idx > 0)
    cerr << ", ";
  else
    cerr << "Line(" << LINE_NUM << ") ";
  stringstream ss;
  ss << H;
  cerr << args[idx] << " = " << ss.str();
  debug_out(args, idx + 1, LINE_NUM, T...);
}
clock_t startTime;
double getCurrentTime() {
  return (double)(clock() - startTime) / CLOCKS_PER_SEC;
}
long long sq(long long a) { return a * a; }
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long dist = sq(x1 - x2) + sq(y1 - y2), i = 0;
  r *= 2;
  while (sq(r * i) < dist) {
    i++;
  }
  cout << i << "\n";
  return 0;
}
