#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x, y, first, second;
  cin >> r >> x >> y >> first >> second;
  long long d = (x - first) * (x - first) + (y - second) * (y - second);
  double dis = sqrt((double)d);
  long long R = 2ll * r;
  long long step = dis / R;
  double rem = (double)dis - (double)R * (double)step;
  if (rem > 0.0000001) {
    if (rem < (double)r)
      step++;
    else
      step += 2ll;
  }
  cout << step << endl;
  return 0;
}
