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