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