#include <bits/stdc++.h>
using namespace std;
double distanceBetweenTwoPoints(double x, double y, double a, double b) {
  return sqrt((x - a) * (x - a) + (y - b) * (y - b));
}
int main() {
  int r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  double dist = distanceBetweenTwoPoints(x, y, x2, y2);
  cout << ceil(dist / (2 * r)) << endl;
  return 0;
}
