#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double R = sqrt(pow(x1 - x, 2) + pow(y1 - y, 2));
  cout << fixed << setprecision(0) << ceil(R / (2 * r));
  return 0;
}
