#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  double length = sqrt(((x - x2) * (x - x2)) + ((y - y2) * (y - y2)));
  int result = ceil(length / (2 * r));
  cout << result << endl;
}
