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