#include <bits/stdc++.h>
using namespace std;
int main(void) {
  cout.sync_with_stdio(false);
  cin.sync_with_stdio(false);
  double x1, y1, r, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double a = sqrt(pow(x2 - x1, 2.0) + pow(y2 - y1, 2.0));
  cout << ceil(a / (2.0 * r)) << endl;
}
