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