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