#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int x, y, nx, ny;
  long long int r;
  double d;
  cin >> r >> x >> y >> nx >> ny;
  d = pow(((nx - x) * (nx - x) + (ny - y) * (ny - y)), 0.5);
  r = 2 * r;
  d = ceil(d / r);
  cout << d << endl;
}
