#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  long long int mx, my;
  long long int distance;
  long long int answer;
  mx = abs(x2 - x);
  my = abs(y2 - y);
  mx *= mx;
  my *= my;
  distance = sqrt(mx + my);
  if (distance * distance != mx + my) {
    answer = (distance / (2 * r)) + 1;
  } else {
    answer = distance / (2 * r);
    if (distance % (2 * r) > 0) answer++;
  }
  cout << answer;
  return 0;
}
