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