#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double p = sqrt(((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)));
  cout << ceil(p / (2 * r));
  return 0;
}
