#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
  cout << (int)ceil(d / (2 * r));
  return 0;
}
