#include <bits/stdc++.h>
using namespace std;
int main() {
  std::cout << std::fixed;
  std::cout << std::setprecision(20);
  long long int r, x, y, x_new, y_new;
  cin >> r >> x >> y >> x_new >> y_new;
  double dist = sqrt(((x_new - x) * (x_new - x)) + ((y_new - y) * (y_new - y)));
  long long int ans;
  ans = ceil(dist / (2.0 * r));
  cout << ans << endl;
}
