#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  float p;
  p = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  p = p / float(r);
  p = p / 2;
  p = ceil(p);
  cout << p;
}
