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