#include <bits/stdc++.h>
using namespace std;
int r, x, y, c, d, dist;
int main() {
  srand(time(NULL));
  cin >> r >> x >> y >> c >> d;
  double dist = sqrt(((x - c) * (x - c)) + ((y - d) * (y - d))) / (2. * r);
  if (dist - (int)(dist) > 0)
    cout << (int)(dist) + int(1);
  else
    cout << (int)(dist);
}
