#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double dis = sqrt(float(pow(abs(x1 - x), 2)) + pow(abs(y1 - y), 2));
  cout << ceil(dis / (2 * r));
}
