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