#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  if (x == x2 && y == y2)
    cout << 0;
  else {
    double shokalata = sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y));
    double candy = shokalata / (2.0 * r);
    int halawa = shokalata / (2.0 * r);
    if (candy > halawa) {
      cout << halawa + 1 << endl;
    } else {
      cout << halawa << endl;
    }
  }
  return 0;
}
