#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1, l;
  cin >> r >> x >> y >> x1 >> y1;
  l = int(
      (sqrt((double)(abs(x1 - x) * abs(x1 - x) + abs(y1 - y) * abs(y1 - y))) /
       (2 * r)));
  if ((sqrt((double)(abs(x1 - x) * abs(x1 - x) + abs(y1 - y) * abs(y1 - y))) /
       (2 * r)) > double(l))
    l++;
  cout << l << endl;
  return 0;
}
