#include <bits/stdc++.h>
using namespace std;
template <typename T>
void _f(const char* name, T&& arg) {
  cout << name << ": " << arg << '\n';
}
template <typename T, typename... Args>
void _f(const char* names, T&& arg, Args&&... args) {
  const char* split = strchr(names + 1, ',');
  cout.write(names, split - names) << ": " << arg << " |";
  _f(split, args...);
}
double tick() {
  static clock_t oldtick;
  clock_t newtick = clock();
  double diff = 1.0 * (newtick - oldtick) / CLOCKS_PER_SEC;
  oldtick = newtick;
  return diff;
}
int main(int argc, char** argv) {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.precision(5);
  cout << fixed;
  long long r, x, y, dx, dy;
  cin >> r >> x >> y >> dx >> dy;
  long long dd = (x - dx) * (x - dx) + (y - dy) * (y - dy);
  double d = sqrt(dd) / (2 * r);
  if (d == (int)d)
    cout << ((int)d) << '\n';
  else
    cout << ((int)d + 1) << '\n';
  return 0;
}
