#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt(abs(x - x1) * abs(x - x1) + abs(y - y1) * abs(y - y1));
  int e = 2 * r;
  cout << ceil(d / e);
}
