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