#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double long disx = ((abs(x1 - x2)) * (abs(x1 - x2)));
  double long disy = ((abs(y1 - y2)) * (abs(y1 - y2)));
  double long diss = sqrt(disx + disy);
  cout << ceil(diss / (2 * r)) << endl;
}
