#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1);
const long long mod = 1e9 + 7;
int main() {
  ios_base::sync_with_stdio(false);
  cout.tie(NULL);
  cin.tie(NULL);
  ;
  double r, x1, y1, x2, y2, n, m;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  n = sqrt(((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)));
  cout << ceil(n / (2 * r));
  return 0;
}
