#include <bits/stdc++.h>
using namespace std;
int main() {
  long r, x1, y1, x2, y2;
  double q;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  q = sqrt((pow(y2 - y1, 2.0)) + (pow(x2 - x1, 2.0)));
  cout << ceil((q / r / 2)) << endl;
  return 0;
}
