#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  double s;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double l = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  s = l / 2 / r;
  if (s == int(s))
    cout << s;
  else
    cout << int(s) + 1;
  return 0;
}
