#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1, dist = 0;
  cin >> r >> x >> y >> x1 >> y1;
  dist = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  dist = sqrt(dist);
  dist /= (r * 2);
  int ans = (int)ceil(dist);
  cout << ans << endl;
  return 0;
}
