#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) + 1;
  else
    cout << int(dist);
}
