#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt(abs((x1 - x) * (x1 - x)) + abs((y1 - y) * (y1 - y)));
  r = r * 2;
  cout << ceil(d / r) << endl;
  return 0;
}
