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