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