#include <bits/stdc++.h>
using namespace std;
const int OO = (int)1e6;
const double EPS = (1e-11);
int dcmp(double x, double y) { return fabs(x - y) <= EPS ? 0 : x < y ? -1 : 1; }
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  r = 2 * r;
  int ans = ceil(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)));
  int anss = ans / r + EPS;
  if (ans % r != 0) {
    cout << anss + 1 << endl;
  } else {
    cout << ans / r << endl;
  }
  return 0;
}
