#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double Distance = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  int result = ceil(Distance / (2 * r));
  cout << result;
  return 0;
}
