#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1, a, ans;
  cin >> r >> x >> y >> x1 >> y1;
  a = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  if (a / (2 * r) != (int)a / (2 * r))
    ans = (int)a / (2 * r) + 1;
  else
    ans = (int)a / (2 * r);
  cout << ans;
}
