#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  float dist = sqrt(pow((x - a), 2) + pow((y - b), 2));
  if (dist == 0)
    cout << "0";
  else
    cout << ceil(dist / (2 * r));
}
