#include <bits/stdc++.h>
using namespace std;
int main() {
  double i, j, n, x1, y1, x2, y2, r, dis;
  long m;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  r = 2 * r;
  dis = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  m = dis / r;
  if (dis - (m * r) > 0) m++;
  cout << m << endl;
  return 0;
}
