#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int r, x0, y0, x1, y1;
  cin >> r >> x0 >> y0 >> x1 >> y1;
  float dist = float(sqrt(pow(x1 - x0, 2) + pow(y1 - y0, 2)));
  cout << ceil(dist / (2 * r));
}
