#include <bits/stdc++.h>
using namespace std;
int main() {
  double x1, x2, y1, y2, r;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double distance = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  int minSteps = int(distance / (2 * r));
  if (distance / (2 * r) > minSteps)
    cout << minSteps + 1 << endl;
  else
    cout << minSteps << endl;
}
